ANNO: Mutationem: Ann often looked out for her younger brother Ryan whenever he got bullied and got him out of a bad situation when he almost fell in with the wrong crowd. After Ryan goes missing, she sets off to find him.
Ezio Auditore da Firenze. In Assassin's Creed II, the first few missions you get involve helping his infirm little brother Petrucio, and beating the crap out of his sister Claudia'sJerkass boyfriend Duccio. Petrucio's wrongful murder (along with that of his father and older brother) is actually what starts Ezio down the path of the Assassin. For added humor, Ducio turns up years later in Brotherhood, still talking trash about Claudia, and Ezio gets to beat him up again. He also has a cameo in Revelations. This time, the mere sight of Ezio sends him fleeing in terror.
The Eagle Bearer, protagonist of Assassin's Creed: Odysseynote The game has two playable protagonists, Alexios and Kassandra. Whoever is chosen by the player becomes the Eagle Bearer and eldest sibling, while the other one will become Arc Villain of the main campaign, Deimos, and the younger sibling. Their first kill, executed when they were seven years old (according to the canonical novel), was against a Spartan Elder who was about to drop their baby sibling off of a cliff as a human sacrifice. 20+ years later, they remain angry about their inability to save their sibling and resentful towards those who did the deed. Their actions are dictated by the player, but it's very much an option for this protective instinct to remain when their sibling reappears, having survived their fall but having spent their life as a brainwashed soilder of the very cult who orchestrated their sacrifice when they were a baby.
They additionally have come to see a Street Urchin named Phiobe as their surrogate little sister, and the absolute quickest way to rile them up is to threaten her. When she is later killed by cultists, there is no mercy to be had for the ones responsible.
In Baldur's Gate II, the Player Character gets to be this for Imoen who is your character's actual half-sister all along, as you discover. Granted, you can choose dialogue options that indicate you don't really care, but you still have to rescue her from Spellhold. If you play the game as a good character, though, you are this trope in spades.
This is the driving force behind the original game, with Banjo stopping at nothing to rescue his sister Tooty from Grunty.
While it is never addressed in the game itself, Jamjars from Banjo-Tooie is Bottles' older brother. His motive for teaching Banjo and Kazooie new moves in the game is to assist them in their quest to bring Bottles Back from the Dead after Grunty kills him.
The Big Daddies and Little Sisters in BioShock are based directly on this trope. The Big Daddies are massive cyborgs that have been programmed to always watch over the Little Sisters and protect them at all costs, while the Little Sisters are conditioned to always stay close to a Big Daddy and rely on them for protection. Neither Big Daddies nor Little Sisters are aggressive and attack on their own, but unfortunately you need the ADAM the Little Sisters extract from corpses with huge syringes, which they don't give up willingly. And when somebody touches a Little Sister her Big Daddy will fight to the death.
BioShock 2 goes even further and puts you in the role of a Big Daddy whose Little Sister was taken away and who had been dead for 10 years. When he is revived, the Little Sister Eleanor calls for his help to rescue her from her mother's imprisonment. For most of the game you put half of Rapture upside down and tear through hordes of splicers to get back to her and save her.
As a Big Daddy you also have the ability to adopt other Little Sisters and have them harvest ADAM for you. This leaves them vulnerable to attacks from splicers for about a minute during which you crush the skull of anyone who is trying to attack her.
BlazBlue had Ragna doing this for Saya. When she was sick he always spent his time with her.
He did this for Jin as well, despite Jin wanting to show his "love" by killing his brother. Several times Ragna could have killed Jin, but he doesn't, as well as saving Jin's ungrateful ass several times.
He also does this for Noel after she absorbs Izanami and becomes more like Saya. ''This'' video shows Ragna caring for Noel, it also crosses into My Sister Is Off-Limits
Despite being turned into a robotic battle doll Nirvana/Ada Clover still shows this towards her little brother Carl. This translates in Carl's moveset being based around controling both him and Nirvana to fight.
Raul Menendez from Call of Duty: Black Ops II is a Dark Messiah who plans to completely overthrow the First World for his sister Josephina, who was badly scarred in a warehouse fire caused by its American owner for insurance money and later was accidentally killed during a CIA raid on Menendez's home in Nicaragua. Even some 30-40 years after the fact, he is still fighting to avenge her. In a brief moment when you actually play as Menendez, he turns into a One-Man Army (even by COD standards) on a Roaring Rampage of Rescue in a desperate bid to rescue Josephina from his burning mansion. Just before this, he bluntly warns a Panamanian soldier that he'll kill him if he so much as lays a finger on his sister, and he was not exaggerating.
King from Cave Story has is this towards Toroko. He gets angry when she refuses to give him the key to Arthur's house, but will also fly into a rage when she gets kidnapped (and that's without touching red flowers, either).
Inverted for Clementine in Chicory: A Colorful Tale. Upon hearing that her older sibling Pizza was insulted by a manifestation of Chicory's anxiety in Gulp Swamp, she asks them if she should beat Chicory up for it.
Corpse Party has Satoshi Mochida, who has this for his younger sister Yuka. Yuuya Kizami, who Yuka meets after she and Satoshi are separated, is also looking for his younger sister. Except he doesn't have a younger sister and is, in fact, a subversion.
Crash Bandicoot for the most part is a mellow Cloud Cuckoo Lander with a pitiful attention span. However, he will go through Cortex and every single one of his mooks should they mess with his little sister, Coco. Uka Uka boasting his intention to destroy her once she has outlived her usefulness for his current scheme is about the one point Crash takes the fearsome ancient god mask seriously.
Agent Brown mixes this with Vitriolic Best Buds in the Detectives United series. He's indicated to be older than fellow detective James, and he snarks at the other man as often as not. But they like each other a lot, and Brown doesn't take it well if James gets himself into trouble. This gets fully illustrated in the fourth installment, in which Brown tackles his real brother (his Evil Twin) to the floor to prevent him from attacking James. Anna, their third partner, has similar protective instincts but is slightly more reserved about expressing them.
Zig-zagged in Devil May Cry as Dante and Aloof Big Brother Vergil alternate between showing care for each other and trying to slice each other to pieces when they meet. Even when Brainwashed and Crazy in the first game, Vergil (aka Nelo Angelo at the time) fought against Mundus’s control when he realized he was fighting his brother. In the third game Vergil, despite his apathy, forgoes multiple opportunities to finish off Dante, only wanting his brother’s amulet. Though, he was prepared to kill Dante when he learned he needed his brother’s blood to open the gate to the demon world. However, Vergil still stepped in to help Dante in the Final Battle against Arkham.
Dante plays this straighter; his hatred of Mundus is fueled by what he did to Vergil as well as killing his mother Eva. In DMC3, despite their hostility, Dante reached his hand out to stop Vergil from falling off a cliff into the demon world, and at the end, Lady spots Manly Tears which Dante tries to hide upon reflecting on the loss of his brother. Averted in DMC5. Brothers they may be, Dante won’t stand for Vergil hurting his son (and Dante’s nephew) Nero and unlike their last confrontation, Dante is perfectly willing to kill his brother for the world’s sake. However, in The Stinger Dante and Vergil have rekindled their brotherly bond, having sparring matches in the Demon World.
Played straight with literal Knight Templar Big Brother Credo and his little sister Kyrie in DMC4 as Credo was completely onboard with Sanctus‘s plan...until he captured Kyrie. Then, all bets were off and he tried to kill Sanctus without a second thought. Considering Nero was raised in Credo and Kyrie’s family, Credo’s attitude towards Nero in the early parts of the game has shades of this.
There’s also the inverse as the only time Kyrie stops loving Nero is when she thought he was about to kill Credo in cold blood.
In Disgaea Dimension 2, Laharl gradually develops this towards Sicily even before Seraph Lamington reveals that she truly is Laharl's little sister. The primary conflict of the game is also due to this. Xenolith bonded himself to a magic draining Artifact of Death to save his little sister Etna from being killed by her own magic. Said artifact is also draining the Netherworld of magic, and Xenolith kidnapped angels so he could use their power to keep the Netherworld from dying. Xenolith fights to prevent the artifact from being destroyed because doing so would return Etna's magic to her, and he's afraid that it will kill Etna. In one Bad Ending, his fears are confirmed.
Zed from Disgaea 6: Defiance of Destiny has undying loyalty as a brother to Bieko, even if they aren't blood related. He even says a big brother's sole purpose of existence is to protect their little sisters. The whole reason Zed was willing to go through countless Super Reincarnations and defeats at the hands of the God of Destruction was for Bieko's sake and to Mercy Kill her when Cerberus told him there's no way to undo her transformation into the God of Destruction.
And to really drive this trope's point, this game has Evilities specifically related to little sisters and older siblings.
The Dwarf Commoner Warden displays this many times when their older sister is involved. Given how depressinglife is for Casteless dwarves, it's easy to see why this is the case, at least before the Warden is recruited by Duncan.
The City Elf Warden can behave similarly toward their cousins, for pretty much the same reasons.
Merrill, the ridiculously cute and adorably awkward bloodmage of the party seems to have the power to instill this in those around her. Half the party actively looks out for her, especially the amoral pirate captain and the dwarven spymaster, and Anders starts to look out for her, in his own extremist blood magic-hating way. The only one who truly dislikes her is Fenris, and he tries to get her to change her ways, albeit in the only way he knows how. Even Hawke can easily turn into this if s/he doesn't romance her.
Bethany Hawke as well. The first thing Hawke does when they meet Wesley is to give the Templar a Death Glare, before he makes clear his intentions. This is the reason her relationship meter is heavily tilted toward "friend" — that, and her baaad case of Big Brother Worship (not that the two are unconnected). In playthroughs where they actually meet, Varric also dotes on Bethany and has a similar protective instinct, though he has fewer opportunities to show it; he does, however, frequently display this attitude toward Hawke, for whom he has Undying Loyalty.
Carver shows glimpses of Little Brother Instinct, through it seems to be buried under a thick layer of Sibling Rivalry. He won't let Fenris threaten Hawke in his presence, and will be highly antagonistic towards Sebastian if he marries his sister.
Varric still has this for Hawke in Inquisition, and also has some shades of it toward the player character, who has been to hell and back (almost literally); notably, he's one of the only characters in the entire game to ever check if the Herald is okay.
Cole inspires feelings of this nature in a few of the companions, most particularly Varric, Solas, and the Iron Bull. Depending on player reactions, the Inquisitor can have this for him as well.
Iron Bull: You may be a weird, squirrelly kid, but you're my weird, squirrelly kid.
Jade from Dragon Quest XI is very protective of the Luminary, as his mother had been her Parental Substitute and she spent 16 years thinking he was dead. One of their first scenes together after she realizes who he is involves her jumping after him when he falls off a cliff and using her body to shield him from the impact. You wouldn't know from watching that scene that she has severe acrophobia.
Dyztopia: Post-Human RPG: Edgar is very protective of his siblings Runi and Rosie. If Akira doesn't reconcile with Runi, Edgar will refuse to enter a romantic relationship with them, even at a high link level. Edgar will also kill Clyde at the first available opportunity because the latter mind-wiped Rosie. This means if he escapes Morgalia before entering Sho's studio, he will kill Clyde at Sho's studio instead of at Aquarius's temple.
Echocalypse: The protagonist makes good points in ensuring their little sister Rayna is safe and when she gets sealed in crystal, they seek to find the means that will set her free.
In Ensemble Stars!, it's generally taken for granted that older characters will feel this towards younger ones, particularly those in their unit and club, but there are some especially notable examples:
The clearest example is probably Kuro, who is first revealed to be much kinder than he looks when he tells Anzu about his younger sister - since their mother died a few years ago, their father has been constantly working in order to support them, so Kuro had a Promotion to Parent to look after her. He comes to think of Anzu as a younger sister as well and is very protective of her, becoming very angry at Madara when the latter seems to put her in danger for his own purposes. He's also a Big Brother Mentor to his unit and club juniors Souma and Tetora, describing them as being like his sons.
Rei and Hinata both dearly love their younger brothers Ritsu and Yuuta (though Hinata is only the elder by a couple of minutes), but aren't shown nearly so much affection back - Ritsu outright dislikes his brother due to feeling failed by him, while Yuuta simply struggles with being seen as only part of a whole due to them being twins.
Other characters with offscreen younger siblings include Leo (a sister, and a crossover character from Ensemble Girls, Hajime (both a brother and sister), and Souma (a rarely-referenced younger brother). Despite being a second year Souma rarely gets to show this side as the majority of his friends are older than him, but when he gets to spend time with Shinobu he proves himself a very capable Big Brother Mentor.
Keito is also described by Eichi as being soft on his juniors, despite his strict appearance. He also refers to Souma as his son (despite only one school year separating them, most likely to increase the Ho Yay with fellow dad Kuro) and takes mentoring his Student Council juniors very seriously.
Nazuna is another character with strangely fatherly impulses, seeing himself as the dad to each of the first-year members of Ra*bits; he even asks them to call him Niichan, a reference to both his surname Nito and this trope.
Eichi and Ritsu both love to dote on Hajime and encourage him to refer to them as Oniisan. He's too intimidated by them both (for different reasons) at first, but eventually does so. And Hajime seems to induce this a lot, as even Kaoru who usually tries to avoid close relationships with other guys eventually comes to think of him as like a younger brother.
Mitsuru is another character who attracts this — he's the baby brother of the Track Team, and it's revealed in one story that he even thinks of Tomoya and Hajime as being an older brother and sister to him, despite being in the same year. (He also has older siblings at home as well.)
The player character herself has a younger brother, and comes to feel this way about a number of the first-year characters; in Scroll of the Elements she explicitly hugs Shinobu because he reminds her of her brother, though while he doesn't mind her acting like a sister, he wants to be seen as his own person and not merely a replacement.
Makoto and Izumi used to have this kind of relationship, with Makoto seeing Izumi as an older brother, but at some point it became twisted and Izumi is now an obsessive, stalking Yandere, while Makoto is basically terrified of him. Over the course of the year their relationship becomes a bit better, but Izumi never gets Makoto to think of or refer to him as an oniichan again.
Chiaki tries to be this to his juniors, but they typically find him overly clingy, loud, and annoying instead. They all do care about him deep down though, and Subaru even compares him to a dad in one story.
Leon from Final Fantasy II despite being a Fallen Hero, genuinely loves and cares for his sister Maria (who can normally look out for herself), he even fought off Imperial Soldiers to defend her as she escaped with Firion. He manages to have a Heel–Face Turn at the end of the game, thanks to his continued care for his sister and his former allies.
Bartz in Final Fantasy V shows this towards Krile, when she joins the party after her grandfather's death. He doesn't treat her as weaker or in need of protection, but he does keep an eye on her to make sure she's okay emotionally. Faris is also very protective of Lenna, even before acknowledging their relation.
Edgar and Sabin from Final Fantasy VI trade off care for each other, Sabin is the younger brother and can definitely look after himself but Edgar would still do anything for his bro while Sabin would do likewise, to extent where he gave up his claim to the kingdom in a coin toss to make Edgar happy. Sabin also displays this instinct towards Gau, Relm and Terra, giving Ultros a beatdown when he grabs Terra with his Naughty Tentacles and is furious at Gau’s father for rejecting his son.
Locke also displays a Big Brother Instinct to Terra especially at the start of the game, doing his upmost to protect her.
This is Cloud’s attitude towards Wedge and Jessie, he acts aloof to them but as seen on missions for AVLANCHE he genuinely cares for their safety and was willingly to kill Johnny over ratting out Jessie to Shinra. Cloud also has big brother instinct towards Marlene, Denzel as well as Tifa and Aerith although his feelings for the latter two girls can be read as a bit more than brotherly.
Barret in Remake display this trait overlapping Papa Wolf to his younger allies, as he greatly cares for Tifa, Biggs, Wedge and Jessie as much as he does for Marlene. He even throws Tifa over his shoulder when she refuses to leave Cloud as he’s dangling from a girder after the Airbuster fight. Barret even has some shades of this towards Cloud himself (despite their bickering) although he of course won’t admit it.
This is Zack’s whole deal with Cloud as well as seen in flashbacks and expanded material like Crisis Core, acting as Big Brother Mentor to Cloud he looks out for him constantly to the point of saving him from Hojo’s experiments and even taking on a squad of Shinra troops to protect Cloud, resulting in his death.
Surprisingly in Remake, Aerith despite being physically weaker display shades of this towards Tifa (which does make some sense she’s two years older) as seen in the Train Graveyard where Tifa is scared, Aerith tells Tifa to hold onto her. Tifa returns the favour during the Eligor fight when Aerith is having Heroic BSoD mid-battle due to childhood visions, leaping in to save her from a laser fired by Eligor. They both also display this to Marlene.
In Remake’s Intergrade DLC newcomer Sonon is like this to Yuffie, although they butt heads throughout their mission he does cares about her and reveals she reminds him of his late sister Melphie who died at the end of Wutai War. He even dies protecting Yuffie from the Ax-CrazySuper-Soldier Nero.
In Final Fantasy X Wakka can’t help but have these instincts towards Tidus since the latter reminds him so much of his late brother Chappu. Lulu has Big Sister Instincts towards Yuna and Rikku, indeed both she and Wakka raised Yuna after her parents died, depending on Relationship Values Lulu can display this to Tidus too despite finding him irritating. Tidus himself has brotherly Instincts towards Rikku, to point of protecting her from Wakku’s Fantastic Racism. Auron and Kimahri also both display this towards Yuna, Tidus and Rikku but they’re more a case of Papa Wolf.
Lightning — soldier, all around badass, and (most importantly) big sister. Her protective relationship with Hope also serves as the plot device that sets up her defrostingprocess.
Snow is also extremely protective of Hope. Post Chapter 7, the only reason Snow will not be the one protecting/comforting Hope is if Lightning got there first.
If you don't see them as romantic, Fang's overwhelming desire to save Vanille from turning into a Cie'th can be interpreted this way; bonus points for Vanille being visibly much younger and weaker in addition to being the cheeriest, cutest, and most tragic character of the cast.
Final Fantasy Tactics: Ramza saving his little sister Alma drives him for the entire second half of the game.
Final Fantasy Tactics Advance: At least after Marche said he will take care of his brother Doned at the real world after they beat his group up at some cave.
In Fire Emblem: The Binding Blade, Zeiss is protected by his big sister Milady, the capable leader of Princess Guinivere's Praetorian Guard, from the dangers of the battlefield in their C support, but he doesn't like it. He wants to be the one protecting her. He does eventually in their A support.
In Fire Emblem: Awakening, the Child Mage Ricken is one of the younger members of the Shepherds, meaning he evokes this trope in many of his allies. Bonus to Henry the Black Mage, who at one point states pointblank that if Ricken was ever cut down (which could be taken as either outright killed or just severely injured), he would decorate the battlefield with the blood of those who did it. Ricken is startled by the statement, for several reasons, but is still quite touched.
Chrom also displays this for his little sister, Lissa - when the Risen first appear, he tells Lissa to run for it while he holds them off. Bear in mind these are mysterious undead enemies he's never seen before and he didn't hesitate to try and buy his sister time. He is also very displeased in his B-Support when he finds out Lissa was sneaking out alone to spy on their enemies because she wanted to feel useful.
Prince Siegbert develops this towards his cousin Prince Forrest, to the point of being overprotective. Their supports are all about Forrest telling Siegbert that he needs more space.
Prince Takumi has this in spades for his little sister Sakura. He is always ready to reassure her whenever she feels distressed and in Conquest his hatred of the protagonist intensifies by a lot when he hears their army has captured her.
In Fire Emblem Echoes: Shadows of Valentia, the Masked Knight Conrad has a little sister and woe betide anyone who threatens her. Said sister is none other than Celica/Anthiese: they were separated after Desaix killed their father and the rest of the Zofian Royal Children, and Conrad trained under the sage Halcyon specifically to reunite with and protect her.
Palla and Catria are both very protective of Est and join Celica's party to rescue her from Garth's stronghold when she is captured by him.
Though we never meet him in person, Holtz, Hilda's big brother, is described as being very doting towards his younger sister, constantly sending her letters and fretting over her wellbeing, much to Hilda's exasperation. Claude even mentions when introducing Hilda that her father and brother coddle her so much that it's why she's the Lazy Bum she is today.
Ashe states that he was forced to become a thief in order to support his younger siblings and the reason he became Lord Lonato's ward is because Lonato caught Ashe trying to rob his house and took pity on the boy.
Raphael is very protective of his little sister, Maya, which also transfers onto the youngest member of his school's House, Lysithea, much to her annoyance.
Seteth is extremely protective of his younger sister Flayn, which frustrates her as he instantly assumes the worst of anyone trying to befriend her (especially boys). The Reveal is that he's not her annoying big brother, but her Boyfriend-Blocking Dad.
Inverted in the case of Jeritza — born Emile — for his elder sister Mercedes. Baron Bartels, the stepfather of Mercedes and birth father of Emile, was an abusive man who drove Mercedes and Emile's mother away into the Kingdom. Later, Baron Bartels learned that Mercedes inherited a Crest from her mother. With her mother past childbearing age, Bartels intended to force Mercedes into marriage in the hopes of siring his own Crest-bearing heir. Upon learning of this, Emile suffered a psychotic break and murdered Bartels. If the player joins Edelgard's coup and had recruited Mercedes to the Black Eagle house beforehand, Jeritza can continue to look over Mercedes; otherwise, he tries to distance himself from her for fear that his violent split personality, the Death Knight, may harm her.
Kratos from the God of War series. When Ares and Athena showed up to kidnap his brother Deimos in God of War: Ghost of Sparta, he, despite being a little kid at the time, actually tried to attack Ares directly to save Deimos.
King Volcheck of Golden Sun: Dark Dawn does not actually have much on screen interaction with his sister, PrincessSveta, that is until he is transformed into a monster and loses his memory. His final act is to push her away from certain death, at the cost of his own life.
In Heroes of Might and Magic, Archibald Ironfist felt this way towards his little brother Roland despite their civil war. In his non-canon ending, Archibald is content with imprisoning Roland for life rather than kill him. In a later game, Archibald helps to rescue Roland since he can't bear to leave his brother in the hands of the Kreegans, all the while knowing that Roland's wife Catherine will be all too happy to execute him. However, Roland convinces Catherine to exile Archibald to an island instead.
Ib: Garry is quick to develop this towards the titular little girl when they meet in the alternate gallery. Garry will be quick to both protect her from harm and help her when she finds words she doesn't understand. In certian routes he's even willing to exchange the rose that represents his remaining life in order to recover Ib's.
Infinite Space has Yuri towards his little sister Kira (perhaps a bit too much). There is also Teodoro, who is very protective to his brother, Adolfo.
Gouenji from Inazuma Eleven acts very protective of his little sister and when some strange guys threaten him to hurt her if he scores a goal against Gemini Storm, he misses the goal intentionally and is dropped of the team as a result for most of the second game. Kidou is this to an even greater extent, reaching Knight Templar Big Brother levels.
Axel towards Roxas, after he started essentially raising the amnesiac Nobody. Sort of a Knight Templar Big Brother, given how much of a Psycho Supporter he is. Often misinterpreted as Ho Yay since the whole "raising Roxas" wasn't shown until a sequel released several years after the game where the Big Brother Instinct was initially shown.
In the prequel game Birth by Sleep, Terra has this towards Ventus. Threaten a hair on that kid's head and it doesn't matter if you're Master Eraqus, he'll still beat you into the ground.
Riku towards Sora, as shown in Dream Drop Distance, when finding out that Sora's heart was in danger.
Sora himself shows this side with Pinocchio as he spends the entirety of Monstro trying to save him either from Riku or The Heartless.
Adelheid Bernstein will do absolutely anything to protect his little sister Rose, as he vows himself to protect her no matter what the cost. This is specially poignant at the end of XIII's Story Mode — which is complete with a CG of Rose falling into his arms when she is freed from Botan's control after Ash erases himself from his existence. The quote illustrates this:
"To protect Rose as her brother — that is his role. It would never change, come hell and high water... In the end his memory was completely gone, but a strong sense of fulfillment remained. Adelheid succeeded in protecting Rose."
Billy Kane has this in regards to his younger sister Lilly, who doubles as his Morality Pet and he absolutely hates it when people bring her up and even try to use her existence as an argument as to why he should leave Geese Howard's service. Athena and Kim learn this the hard way KoF XIII: Climax when they bring her up in pre-fight talks and the usually just cocky Billy YELLS at them to not mention her.
Ryo is very protective of his kid sister, Yuri. This was the reason he initially objected to her taking up Kyokugenryu, and is also the reason he and their fatherwon't let Robert near her, which annoys her to no end. This has been toned down in later games, as he's torn between his desire to protect Yuri and letting her live her own life.
K', with his "sisters" Whip and Kula, despite Whip being technically older than him. And in her case, it's eventually revealed that she is a clone of his older sister Seirah.
Sie Kensou has his own Big Brother Instinct towards his brother figure Bao. Inverted in their team's 2000 ending, when it was Bao who protects Kensou and his teammates by shielding himself from a huge blast from the Zero Cannon and then played straight when Kensou gives him a Kiss of Life to his dying body, which resulted in both saving Bao's life and regaining his lost powers.
Deconstructed with Henry and Sam. Henry is very protective of his little brother, Sam. Because of this, unlike Ellie — who is the same age as him and undeniably a Little Miss Badass - Sam has never been put into a position where he has to fend for himself and thus doesn't know how to fend for himself, making him The Load. In an instance where his brother cannot protect him, Sam is bitten by an infected and turns the next morning, causing Henry to kill himself out of despair. While it's an utterly horrible and Darwinian suggestion, the Infected (and a lot of humans too) ultimately don't care how old you are, so teaching a young child how to fight is a grim necessity in a Crapsack World.
Joel and Tommy display this towards each other, despite Tommy having valid reasons for ditching his older brother after the Joel Jumped Off The Slippery Slope after his daughter Sarah was killed, he still opens the doors of his stronghold town and hugs his bro. Joel likewise cares for his younger brother having apparently helped kept Tommy alive in the years after Sarah’s death although Tommy was horrified at what his brother was willingly to do. It’s most apparent on the sequel when Joel is brutally murdered by Abby while Tommy is Forced to Watch, Tommy goes on his own grief-stricken Roaring Rampage of Revenge sadly mostly off-screen.
The Legend of Heroes: Trails in the Sky: Agate gets very protective of the younger members of the team, especially Tita, who he still looks out for during the Cold Steel games.
The Legend of Heroes: Trails From Zero: Despite being somewhat exasperated by Fran's constant adoration, Noel will always look out for her sister. Noel had an overreaction to finding out that Fran had 'someone she loves'. Said person was, of course, Noel herself.
The Legend of Heroes: Trails through Daybreak: Van acts like a protective older brother towards quite a few younger characters, especially Yume. This somewhat manifests in gameplay through his Draw Aggro craft and his ability to shield one of his party members from an attack as Grendel.
The Legend of Zelda: Majora's Mask: Tatl has this for Tael and Skull Kid. She spends the entire game with Link trying to be reunited with her little brother.
Link has an actual little sister, Aryll, in The Legend of Zelda: The Wind Waker. After she's been taken to The Forsaken Fortress, Link begins his journey to rescue her.
Link acts like this towards the children of Ordon and his friend Ilia in The Legend of Zelda: Twilight Princess. He also receives the same sort of treatment from Rusl, one of the villagers, whom Word of God specifically states considers Link to be his younger brother.
In Hyrule Warriors: Age of Calamity, Mipha's recruitment mission involves Link and the others helping her fend off hordes of monsters invading Zora's Domain while looking for her little brother Sidon. They eventually find him trying to fight a Lynel, and Mipha angrily declares that the monster will not harm him before attacking. Later in the game, it's flipped around with Sidon after being transported from the original timeline whose little brother instinct is on full display to protect his sister from Waterblight Ganon.
In Life Is Strange 2, Sean is very protective of his younger brother Daniel. Sean happens to be the playable character, and much of the player's choices will influence how Sean attempts to take care of Daniel, following the tragic loss of their father.
In the first game, part of Ashley Williams' backstory involves talking a leave of absence to help one of her sisters deal with a clingy ex-boyfriend.
In Mass Effect 2, one of the early signs of the warm person underneath Miranda Lawson's ice-cold exterior is her extreme protectiveness of her younger sister, Oriana. Her subplot in Mass Effect 3 is almost entirely based around her going to the ends of the galaxy to ensure her safety and that their father will never get his hands on her.
Garrus gets a more subtle version of this treatment, but it's still there. If you do the Lair of the Shadow Broker DLC, you can find out that Garrus has a sister, Solana. While we never see a chance for him to be protective of her, he highly values her opinion of him, to the point where he won't talk to her on a video channel so she won't see the gunship injuries, and then have to explain what he did to earn them. While this sours the relationship, he believes the truth would only make her resent him more. Solana's anger likewise suggests she's protective of him as well. In Mass Effect 3, when the last message he receives from his dad is that they made it off Palaven, but Solana was injured in the process, he says a prayer for their safety. For the record, he's not a spiritual man, and doesn't do this for anyone else, not even a romanced Shepard.
Tali rather unsurprisingly invokes these feelings in the other squad members, at least in the first game. Well, she's an adorable and fairly cute Wrench Wench who's the relative youngster on the team. In The Citadel DLC in the third game, it's especially apparent that Wrex in particular feels a certain level of protective affection for her even though he knows she's "all grown up and killing Reapers now."
In Mass Effect: Andromeda, we have Vetra Nyx and her sister Sid. Vetra basically raised Sid, as their father vanished and their mother wanted nothing to do with them. Vetra's loyalty mission involves Sid getting into trouble, and the villain pays dearly for that.
Sara Ryder has this toward her twin brother Scott. The main reason she declares that It's Personal toward the end is because of what the Big Bad did to her brother. Scott is every bit as protective of Sara if he is chosen as the PC, but he's the younger sibling, if only by a minute.
Angara culture emphasizes close family ties, so it is no surprise that Jaal is very protective of his many younger siblings. Jaal's loyalty mission starts off with his attempts to save three of them from doing something stupid.
Invoked by nearly by name in The Matrix: Path of Neo with Neo to an unnamed girl that he has to protect from the Merovingian's mooks.
Bald guy, Elite Mooks: Get the girl, he (the Merovingian) wants to see her. Neo:[As the mooks start to approach] She's not going anywhere with you. Bald guy: What are you, her... big brother ? Neo: Something like that.
Mega Man (Classic): Blues (Proto Man) can be very protective of Rock (Mega Man). He's gone out of his way many times to save his life instead, meaning he keeps an eye on him. He gives a lot of advice to him.
Rock himself is the same way. When Wily reprogrammed his brothers, he became Mega Man, took them down, sent them back to the lab to be reprogramed back to normal, and Then defeated Wily with a BIG LOUD CRUNCH!
And now with Mega Man 10 on it's way, it seems that Mega Man and Proto Man have teamed up to get the vaccine to cure Roll of Roboenza. Whoever created the virus needs to run away now.
Namu Amida Butsu! -UTENA-: While Kannon is already a Team Mom, he is straight-up doting to his brother Seishi. He notoriously maintains a tight control of the temple's finances and pantry and is strict and unforgiving towards any misbehaving Buddhas, even superior tathāgatas, but is nothing but sweet and fluffy towards Seishi.
Ni no Kuni has Gascon and Marcassin, the princes of Hamelin. During their childhood, Gascon was intensely protective of Marcassin, moreso than their actual father, the Emperor, was. Marcassin, in kind, seems to have had quite a bit of little brother instinct as well, as he tried to hide his own magical abilities once he understood that only a wizard could ascend to the throne, and he wanted to make sure his brother got to be Emperor. However, their father died, and Gascon disappeared, leaving Marcassin alone. As it turns out, Gascon is still very much alive... And calling himself Swaine. And he still will not hesitate to kick your ass if you hurt his little brother.
OMORI: Mari displays Big Sister Instinct for Sunny. From little things like taking the blame when Sunny broke their mom's vase, to diving into the lake to save him from drowning (even though there were already others in the water with him), she is highly protective of her little brother. She even had their friend group stop hanging out near the lake, so it could never happen again. Sunny remembers how much she cared for him, and how he felt safe with Mari because he knew she would always protect him.
The main character (whether male or female), Akihiko and Junpei serve as adopted big bros (and sis) to Ken in Persona 3. Akihiko's issues related to his dead sister Miki mean that he also has some protective big brother impulses towards Fuuka and the female protagonist. Shinjiro is similarly protective towards Fuuka and constantly laments what happened in Ken's past.
In Persona 4, the main character acts this way towards Nanako Dojima, which leads to many heartwarming moments. Later in the story, Nanako gets kidnapped and thrown into the TV world, which not only stimulates a response from the main character, but from Yosuke, Chie, Yukiko, Naoto, Kanji, Rise, and Teddie. Unfortunately, if you take this into Knight Templar Big Brother territory and actually throw Nanako's kidnapper Namatame into the TV after her apparent death, it will lead to the worst ending, as Nanako stays dead, and everyone in Inaba gets turned into Shadows.
Persona 4: Arena reinforces this, with the mocking introduction the main character gets in the P-1 Grand Prix video: "Nobody touches his precious Nanako! The Sister-Complex Kingpin of Steel, Yu Narukami!"
A Deconstructed version of this trope occurs in Persona 5 Royal. While the real Kasumi did genuinely care for Sumire to the point of overprotectiveness, this merely caused Sumire to be irritated by her even if she isn't doing it out of Condescending Compassion, because she was simply jealous of Kasumi's superior performances. This resulted in Sumire developing a delusional thought where if she wasn't Kasumi, she should die, eventually accumulating into a fit of running away from Kasumi after practice a month prior to the beginning of Joker's journey, which nearly caused Sumire to be hit by incoming traffic only for Kasumi to push her out of the way and die instead. This becomes a great source of trauma that her parents have to push her to Maruki so he can make her think that she is Kasumi; if not for Maruki's help, she would have been Driven to Suicide from the grief.
In Persona 5 Strikers, all the Phantom Thieves are this towards Sophia, who is the newest Phantom Thief member and an A.I. with little knowledge of but earnest desire to learn about humanity. They are protective and supportive of her and Ryuji and Morgana in particular do not take it kindly at all when at the Okinawa Jail, a mysterious voice and later on, Sophie's creator Ichinose declares Sophia's existence to be a mistake and meaningless.
Pilgrim (RPG Maker): Akemi's entire motivation is to save her little sister Inago from Alice, who has kidnapped her to take her soul. She decides to brave through Alice's castle full of Surreal Horror and deadly traps just to save Inago. She is even willing to make a Heroic Sacrifice and let Alice take her soul if it means Inago gets to live.
Hugh, your rival in Pokémon Black 2 and White 2, is this towards his little sister, whose Purrloin was stolen by Team Plasma 5 years prior to the games. He mows them down at every chance he gets in his search for her stolen Pokémon.
Pokémon Sun and Moon gives us Gladion, who takes off after his sister Lillie when she's kidnapped by Team Skull. What's more, he forces you into a battle out of blind rage when he first hears about it. He does acknowledge afterward that it was wrong of him to act so irrationally, though.
Propagation: Paradise Hotel has the Diaz sisters, Emily and Ashley. It's unknown who's older (being twins), but the player character, Emily, has to fight her way through a Hell Hotel infested by zombies and giant monsters to bring Ashley back.
Luke, in the Professor Layton games, has a bit of a big brother complex toward Flora, despite being very obviously younger. It Makes Sense in Context — Luke's known the Professor for a long time and has assisted in a number of investigations, while Flora is a Fish out of Water in every situation due to her sheltered background, so both Luke and the Professor are protective of her.
[PROTOTYPE]: Mess with Dana Mercer, and your best bet is most likely being eaten alive by big brother Alex. Ironically, the character you play, Virus!Mercer, is a lot more caring about Dana than the real Alex Mercer, who was responsible for the virus in the first place.
Arthur towards John in Red Dead Redemption II. His anger at John leaving the gang for one year can sound like a resentful older brother. Later on, after Arthur is diagnosed with tuberculosis, he subtly tries to coach John on how to do right by his family and what kind of man to be. He risked his life to rescue John from a high security prison when it's strongly implied Dutch would have left him there to hang. He would also try to persuade Dutch to allow John and his family to leave the gang when the gang is becoming too high profile, standing up to Dutch for perhaps for the first time in his life. And a high honor Arthur will protect John when they are being gunned from all sides to get him to safety and will hold off the Pinkertons to buy John time to escape.
Chris Redfield, not only does he go to Antarctica to rescue his sister and save her from Wesker in Resident Evil – Code: Veronica but Chris watches out for the youngest STARS member Rebecca in the first game and saves her from a Hunter. It must be a family trait because his sister Claire basically runs on this ineverythingshe'sdone.
There’s moment in Resident Evil 2 (Remake) when Corrupt Cop Chief Irons has Claire held hostage, as Irons is taking Sherry away Claire threatens that her brother is a S.T.A.R.S officer before Irons cuts her off with a kick. Claire appeared to be implying were Chris to catch wind of Irons’s actions he’d be in for a world of hurt. Of course it’s a empty threat since Chris was in Paris at the time, but it still shows how much faith Claire has in him.
Also from Code Veronica there’s Albert Ashford whose care for his twin sister Alexia reaches disturbing levels and he acted as guardian over her during Alexia’s cryogenic sleep. Alexia returns the favour in brutal fashion after waking up to find her brother dying and cradling Albert’s body, she goes on a Roaring Rampage of Revenge torturing Claire and Steve (the latter of whom she kills).
Resident Evil 2: Leon’s attitude towards little Sherry, though it overlaps with Papa Wolf as he is essentially her surrogate father after William turned into a massive monster and exploded.
Resident Evil 4: Leon sure does go to a lot of trouble for Ashley and seems genuinely compassionate towards her, even if it IS part of his job. Leon is only The Stoic when he's the one in danger, but he'll risk himself without hesitation to protect anyone who needs his help.
Chris once again goes big brother wolf for Rebecca in Resident Evil: Vendetta as he rescues her from Big Bad Glenn Arias (who been stalks and captures Rebecca. Chris beats the shit of Arias before the latter mutates but Chris manages to blow him up with a grenade launcher after Leon arrives to help. Arias is just lucky it was Rebecca instead of Claire he preyed upon otherwise Chris likely would’ve gone apeshit.
The whole premise of Röki is that the main character Tove is setting out to rescue her little brother Lars after a huge monster kidnaps him. To this end, Tove must enter a supernatural realm of spirits and fairies, awaken ancient guardians, and enter a Dark World inhabited by the mother of said monster.
In Shade: Wrath of Angels you're a soldier who travelled through three different circles of hell, each infested with the undead, monsters, and assorted monstrosities, which you slice apart after finding out your younger brother was stranded in their world.
The Simpsons Arcade Game has Bart and to a lesser extent Lisa, both trying to rescue their baby sister going through many enemies in the process. Bart however being the oldest even gets to save Lisa in one of the game's attract sequences when she is grabbed by a fat thug.
Splatoon 2: Though they're cousins, Marie asks Agent 4 in assisting her to locate Callie after she's been taken by The Octarians.
Sonic sometimes takes this role for Cream the Rabbit in several official medias, such as Sonic X.
For a Big Sister Instinct example, Amy is the main one to take this role for Cream.
Less prominently, Big the Cat of all people seems to act this way to his Team Rose comrades in Sonic Heroes. He is shown comforting and defending Cream on several occasions in the story, Team Chaotix intimidating her marks one of the very few occasions he is genuinely pissed.
In general, if Big considers you his friend and thinks you can't adequately defend yourself, then anyone dumb enough to mess with you in his presence is about to get a fishing rod to the face.
Like Amy, Blaze takes a Big Sister Instinct to Cream near the end of Sonic Rush and is also one to Marine in the latter half of Sonic Rush Adventure.
While considered a Bratty Half-Pint, Vector and Espio still act this way to Charmy. Though, Vector may be more of a father toward the honey bee.
Shadow acts this way to Maria before her death in Sonic Adventure 2.
First is Laura, who is herself a borderline bully to her younger brother Sean but she almost attacks Ken thinking Ken was against her little brother.
While not blood related, since Ibuki is The Baby of the Bunch of Karin's squad during Shadowfalls, the older girls take on this role for Ibuki. Karin ensures Ibuki's safety first when the escape helicopter arrives, and Mika literally takes a punch to the face from an man that was aimed directly and specifically for Ibuki.
String Tyrant has a female example. Mary is accompanied by her little brother Lauren and always seeks to protect him. Both Mary and her friend Jessie work to keep him from realizing the danger they are in.
Luigi might have a bit of a "Little Brother Instinct" when it comes to Mario. By that, he plowed through a planet-scale army by himself, with his bare hands, and didn't get hit once because Bowser kidnapped Mario. Later, he overcomes his fear of ghosts to save Mario after he got kidnapped by King Boo. Threetimes. Hell, this is the main theme of Mario & Luigi: Dream Team - no matter what his other impulses might tell him, Luigi will always be there for his big brother.
Mario definitely has a Big Brother Instinct towards Luigi, vouching for his goodness when the Star Gate refuses Luigi entry because of his apparent 'dark past', directing Yoshis to rescue his brother twicewhen they were babies and again, vouching for Luigi in Mario & Luigi: Bowser's Inside Story when Princess Lipid instead assumes that Mario dropped some treasure showing how important his brother is to him. Both brothers sound utterly panicked when the other one goes down in the Mario & Luigi games. And you can see just how much they care for each other in the Mario and Luigi RPGs when they hug each other after overcoming certain trials.
Supplemental material for Team Fortress 2 reveal that the Heavy is this to his sisters (and is also a caring and devoted son to his aging mother). He hunts bears to put food on the table and bodily crushes the men who were hunting his family after he broke them out of The Gulag. He even is willing to turn down a chance to return to his job after being fired, solely so that he can protect them. Turns out he doesn't need to stay to watch over them anymore. His sisters have learned from his example and the men who tried to come for them and their mother while he was away were "butchered like hogs. Their screams died on their lips."
Tokyo Tattoo Girls has Minato Rosa of the opposing Syndicate forces, who never leaves her sister Ortensia's side. This is mainly because Ortensia wasn't gifted a real Power Tattoo during the catastrophe, and is just wearing a fake.
Tokyo Xanadu: Mitsuki gleefully note that Shio is very thoughtful towards his underclassmen, to his embarrassment.
Though their ages are left unstated, Sans from Undertale is canonically older than his brother Papyrus. Sans openly admits that his dorkyand painfullyniceManchild brother is the single coolest person he knows, and he is very protective of Papyrus and his happiness. The only thing that actually gets on his bad side is killing Papyrus in a run-through, which turns him from a wacky side character into someone who disappears from the rest of the game and only appears again in the epilogue, where he judges your actions and leaves you with what amounts to "go to hell". The only reason he doesn't give you a bad time is because of his promise to Toriel. Plus, he's aware you can start another playthrough and thus undo his murder, though naturally he'll still think you're a bastard.
Speaking of a bad time, if the game detects that you're on a genocide route, Sans will warn you prior to the fight with Papyrus to stop killing or you're really not going to like what happens next. If you ignore his warning and make it to the end of a route, he shows up again and, deciding he can't afford to not care anymore, proceeds to utterly pulverize the living daylights out of you. He never references his brother directly while doing this, but examining his dialogue makes it pretty clear that he's on the forefront of his mind - the very first thing he asks you is whether or not you think it's possible for anybody, no matter how evil they are, to be a good person if they just try hard enough, and then laughs before you can give an answer, an Ironic Echo of Papyrus's last words when you murdered him. And if you finally manage to persevere through the battle and kill him, his own last words are telling Papyrus he's going out to eat and asking if he wants him to get him anything, meaning he's either hallucinating or can see his brother waiting for him in the afterlife.
Papyrus also returns a degree of the same instinct toward his brother, even though he's younger and it manifests differently. Despite often acting like Sans is nothing but a nuisance, he never says or does anything genuinely mean-spirited or hurtful toward him and still works hard to keep him productive and healthy in the face of his depression-induced laziness. He's the reason Sans even has a job in the first place, often fusses about his poor life choices over phone calls, and at one point outright tells you that he "doesn't know where he'd be without such a cool guy taking care of him".
Mettaton turns out to be this to his morose cousin Napstablook. Not actually brothers, but he has the same protective instinct; reject the latter's request to be friends and Mettaton will instantly notify you that you're now his nemesis, in spite of the lack of ill will he bears towards you otherwise. Originally Mettaton comes off as extremely self absorbed, but when he realizes what he gave up to achieve stardom, he turns around and goes back to being supportive and caring, while still very self absorbed.
Deconstructed in Until Dawn where Josh's Big Brother Instinct for his sisters managed to bring out the worst in him. The love for his sisters became warped as Josh felt his friends, including Sam and Chris who were the least involved, were responsible for his sisters' deaths and throughout the year, he was driven in his grief and madness to make his friends pay for what they did by humiliating and traumatizing them.
Clementine from The Walking Dead (Telltale) quickly bonds with baby Alvin Junior, and is extremely protective of him. This is flipped with Sarah, where Clem can be fiercely protective of Sarah despite being four years younger.
In Warcraft, Malfurion Stormrage sealed his brother Illidan deep underground for 10,000 years after he endangered the entire world by creating a new Well of Eternity (the Night Elves had just fought a brutal war to destroy the first one since the Burning Legion used it as a gateway to Azeroth) to sate his addiction to magic. Tyrande went against his orders and freed Illidan thinking he would be an asset in the current war with the Legion. Despite all of this, Malfurion's instinctive response when confronting a demon he believes has slain Illidan (unaware that said demon is Illidan after he consumed the power of an Artifact of Doom) is pure rage.
World's End Club: After Aniki sees his sister Vanilla staying behind to prevent Pielope from attacking the others, he decides to stay behind while the others move ahead.
Xenoblade Chronicles 1: Even if it takes her a long and painful trek through an Ether Mine, Sharla will find her brother Juju and she will put a bullet between the eyes of whoever took him.
Xenoblade Chronicles X: Rook has this towards Lin, first seen when L appears. Rook is given the choice to either use Lin as a shield, or protect her by standing in front of her.
In Xenoblade Chronicles 2, this is actually Mòrag's official job as Special Inquisitor of the Empire of Mor Ardain. Her younger cousin Niall is the Emperor, and her duties as Special Inquisitor involve taking charge of his security and investigating other general threats to Mor Ardain.
video shows Ragna caring for Noel, it also crosses into My Sister Is Off-Limits