A side effect of Parental Abandonment that occurs when the trope applies to siblings. The first born takes over the role of parent—enforcing the rules, setting curfews, delivering lectures, and bringing home the paycheck. They may be doing the parents' job, but they are still a brother or sister to everyone else, and will probably get into conflict with their siblings over how much power they should have and how much respect they deserve, depending on the ages of the younger ones, and the status of the original parents (i.e. missing/dead/villains...). The parents may have even specifically asked their eldest child to Take Care of the Kids.
On a positive note, the sibling-parent is usually within the Competence Zone, and will be understanding if you have to Wake Up, Go to School, Save the World. If they get Trapped in Another World themselves, they'll expect to be fully responsible for their charges' safety, even to the point of Heroic Sacrifice. Becoming a sibling-parent often makes a child Wise Beyond Their Years.
Truth in Television, although it's more common on the frontiers of civilization and when families were larger and more spread out in ages. (Westerns make use of this a lot.) Sometimes the oldest kid of a one-parent family tries to take some responsibility off the parent too.
If this takes place on a society-wide level, it's a Teenage Wasteland: the strongest of the survivors, where "strongest" usually equals "oldest", end up taking the younger survivors under their wings, forming pseudo-familial units in which the older kids are the "parents" and the younger ones are "children". Smaller-scale versions include the plane crash that strands a family while killing or incapacitating the parents and the Neverland scenario, in which a bunch of kids have run away from home or are otherwise isolated.
In some rare instances, there are still adults around but children get drafted as a Parental Substitute because of some combination of importance, dangerousness and difficulty. This is generally because only those of "pure heart" or some such can do it, and adults are too corrupted. Thus, this variant is most likely to have the cut-off be puberty. It's kind of the opposite of the Puberty Superpower, with plenty of angst as the kids age towards the cut-off and/or their ability to perform their job wanes with increasing age. In some cases, it's just that the adults are too incompetent to handle the job or the family is just that big, and thus the eldest children end up having to back up Mom and Dad.
This trope can also apply to adults. For instance, when someone childless (likely a man) finds out of the blue that he has a child he didn't know about. This usually can range from the traditional accidental conception ("I'm your daughter/son.") to the scifi clone. Another way would be when a woman finds out she is pregnant and has to step up to being a parent whether or not she is ready for it yet. Still another, when a swinging bachelor/bachelorette uncle/aunt is unexpectedly saddled with guardianship of a nephew/niece.
This trope is almost always present in a Badass and Child Duo.
Compare to Big Brother Instinct, Family Man, and Extremely Protective Child. If this trope is a Klingon Promotion to parent, the promoted will also be a Self-Made Orphan. Contrast with Disappointing Older Sibling when the first born proves to be too immature, irresponsible, or ineffectual to be a parental substitute. Playing House is when it's just a game kids play.
- In Batman's absence, Dick Grayson is forced to take both his mantle and responsibility for the Bat-Family, specifically his little adoptive brother Damian. And since Damian and Bruce clash like crazy, Dick was in this position even after Bruce got back (at least until the reboot).
- Bruce also sort of had this with Tim after Tim's father (his only remaining parent by that point) died. Tim's last name was even changed to Drake-Wayne. Needless to say when Bruce went missing for awhile Tim had issues.
- Bruce not doing this enough is one of the reasons Jason turned out like he did.
- Harper Row is this for her teenage brother Cullen after the two run away from their abusive father.
- In Billy Batson and the Magic of Shazam, Billy (who's about ten) serves this role for his younger sister Mary—the two orphans live alone, using Billy's Older Alter Ego whenever they need a fake parent. (Note that this is different than most Shazam adaptations, where the pair are the same age and both are eventually Happily Adopted by the Bromfields.)
- In Captain Atom #56, it is revealed that after his father left when he was five, and his mother became an almost totally nonfunctional alcoholic, Nathaniel's sister Peggy Ann took care of him and raised him, even though she was only a couple of years older than he.
- Rory and Pandora Destine of ClanDestine were raised by their brother Walter and sister Florence (posing as their uncle and grandmother respectively). This seems to be standard procedure for the Destines; one of the grown-up siblings mentions that he was also raised by an older brother, and even when the family's Disappeared Dad returns, he doesn't take over as the kids' guardian.
- In Fantastic Four, Susan "Sue" Storm was this to her brother Johnny when they were growing up.
- In Impulse, Impulse's friend Carol is being raised by her adult brother after their parents died in an auto accident.
- The Incredibles: A villain named Larry claims to have raised two brothers and three sisters.
- The older kids in Runaways act as parents (or at least supervisors) for Molly and later Klara.
- Superman usually serves this role for his younger cousin Kara Zor-El alias Supergirl -or Power Girl-, who arrives on Earth after losing her parents. Ironically, in the Post-Crisis comics Kara was born earlier and she expected to raise her baby cousin when she arrived on Earth, but her ship was delayed and she was put in suspended animation; when she crash-landed on Earth, Kal was nearly twice her age.
- Empress in Young Justice gets "promoted" to parent when her parents are turned into babies and she has to take care of them.
- X-23 has found herself in the position of having to raise a thirteen year-old clone of herself created by a division of Alchemax. Energetic and precocious Gabby is quite a handful and the pair frequently butt heads, but They Really Do Love Each Other.
- Yakko in the Animaniacs movie Wakko's Wish. He leans toward this trope in the series too, but since the movie takes place in an Alternate Universe where the Warners are actual orphans - unlike in the series, where they never had parents, but were created by an animator drawing them it's especially visible there.
- Big Hero 6: Although Tadashi and Hiro live with their Aunt Cass, Tadashi makes a special effort to fulfill the role of big brother and father figure. It's most obvious when he's distressed over Hiro's botfighting hobby and wonders what their dad would say in that situation. This trope also applies to Aunt Cass who took both boys in when their parents died.
- Elsa in Frozen goes through this with Anna after their parents die. Even though she's barely present in Anna's life for the three years between their parents death and her coronation, isolating herself out of fear of her ice powers, she still takes her responsibility as Anna's legal guardian seriously, as shown when she vetos her marriage to Hans.
- Nani of Lilo & Stitch is Lilo's older sister, who became her legal guardian after their parents died. The two still argue like sisters. Lilo even says, "I like you better as a sister than a mom." Despite knowing about Lilo's mission to find more than 600 aliens scattered about Hawaii, Nani would probably prefer if her little sister had a safer hobby. Nani has forbidden Lilo and Stitch on at least one occasion from using the hovercars that Jumba gave them as a Christmas gift because it's not safe. Additionally, the first film serves as somewhat of a deconstruction of this trope, as it deals with Nani struggling to be a competent guardian and raise Lilo to the satisfaction of Social Services shortly after their parents' death. "Struggling" is really the only way to describe it, and it's heartbreaking watching a loving and well-intentioned sibling having her little sister taken away so soon after losing both of her parents. The sad thing is, it's surprisingly realistic because Nani is nineteen...
- Jane's Promotion To Parent in 27 Dresses is the explanation for her Extreme Doormat tendencies.
- In 30 Days of Night, the parents of Eben and Jake Oleson are never seen or even mentioned, so it's very likely that Eben and his grandmother have shared custody of his teenage brother for quite some time. Once the vampires arrive and their grandmother is killed, he becomes this trope in full-force.
- Benny & Joon: The title characters' parents have died some years before, leaving Benny to raise Joon, who is a mentally Ill Girl. He takes his role very seriously but also objects to options that may have been helpful to Joon, such as sheltered accommodation or her relationship with Sam partly because he doesn't want to lose her.
- Sarah Biederman in Deep Impact is forced into the role as her parents outfit her with carrier, diaper bag, and baby so she and Leo can get safely to high ground before the meteor strike floods and kills everyone at ground level. Sarah's parents don't even bother trying to get to high ground themselves. They just stand there and gaze at each other with resigned affection. That's kinda justified, in that the water was already coming, and the only reason they had the opportunity for her to get to safety is that her boyfriend just showed up on a bike looking for her and they couldn't exactly fit four grown people and a baby on a single bike.
- Don't Tell Mom the Babysitter's Dead: When the elderly babysitter unexpectedly dies, the two oldest siblings are left to manage the household. Sue Ellen has to get a job after their money runs out, while Kenny has to stay at home to take care of the three youngest siblings. Sue later calls out Kenny on behaving pretty irresponsibly himself by ignoring his new role.
- Alexandria in The Fall begins to see Roy as a father figure after her own father's death. In Roy's story, the Black Bandit's daughter starts to call him "Daddy", which eventually angers Roy.
- In Finding Neverland, George, the eldest of the Llewelyn Davies boys, starts taking more responsibility for his brothers as the story goes on, causing James Barrie to comment on him becoming an adult. Fortunately for him, his mother is still alive, albeit ill, and James is also looking after him and his brothers.
- The Hunger Games: Katniss Everdeen for her sister, due to her mother's depression and general ineffectiveness.
- Joy: 8-year-old Az basically becomes the mom after her mother dies in childbirth. She looks after baby Jargal when their father is away, she keeps the family bankroll under her mattress, and she lectures her father about budgeting and keeping track of expenses.
- Peter and Susan Pevensie in The Lion, the Witch, and the Wardrobe, after their parents send them to the country and away from London during World War II. They not only serve as surrogate parents to younger siblings Edmund and Lucy, but try to parent each other. This trope is present in the book, but especially played up in the 2005 film version.
- Love Actually has Sarah's problems in regards with her ill brother after her parents died. Also to a lesser extent, Daniel is left to raise his stepson while trying to deal with his own grief of his wife's death. While he started out as a parent, it was previously a less active role.
- Lucy for the title character in Martha Marcy May Marlene, since it's implied both their parents are dead.
- The oldest brother in the Japanese film Nobody Knows has to care for his three younger siblings after father and mother abandoned them.
- In Our House, Ethan takes over the family home, and takes care of his younger siblings, when his parents die in a car accident.
- The Proposition strongly implies that Arthur raised his younger two brothers largely by himself. This makes him a far more effective Anti-Villain.
- In Real Steel, Charlie Kenton is a deadbeat dad who ends up meeting his son Max for the first time when Max's mother dies and Charlie agrees to look after him for a few months before Max's aunt takes him in. At first, Charlie only agrees to take the kid to get a pay-off from the aunt's wealthy husband while they go on vacation in Italy, but over the course of the film and their restoration of an old robot that they use for fighting, Charlie and Max gradually become closer.
- Lyddie in Saving Sarah Cain. Interestingly there is a special quirk. Sarah is the official guardian of an Amish family despite being an "Englisher" (non Amish). However Lyddie is jealous of her, quite justifiably because she is obviously a supremely competent mother whereas Sarah is selfish (which is of course why she needed to be saved) and unfamiliar with Amish ways.
- In Super Mario Bros., Mario briefly mentions he had to raise his brother Luigi after their parents died. This isn't the case in the games where they're twins and their parents are never mentioned.
- In What's Eating Gilbert Grape, Gilbert's narration describes his older sister, Amy, as more like a mom, and indeed she does most of the household duties; their actual mother, Bonnie, is morbidly obese and rarely moves from the couch, while their father killed himself years before. Gilbert himself seems to be financially supporting the family and takes up most of the responsibility for watching Arnie, their mentally disabled brother. The film ends with Bonnie's death; after a one-year Time Skip, Amy and youngest sister Ellen are moving to Des Moines together with Gilbert and Arnie possibly planning to follow.
- In Winter's Bone, 17 year old Ree is charge of taking care of her siblings as Dad's gone and Mom's sick.
- In The Space Gypsy Adventures, Gemma has been raising her brother Damien since they escaped from a Federal Alliance prison camp following their family's collective arrest for gunrunning. She often acts maternal towards him (unless he's being a mischievous little brat) and has been mistaken for his mother more than once.
- Dawn of a New Age: Oldport Blues:
- After his mother left and his father needed to work full-time, Ciro took on much of the parental responsibilities in regards to his two younger siblings. This has left him with a caring disposition, though it's also made him a habitual worrier who struggles with taking things easy.
- After Hyeon's parents left him and his grandmother passed away, he was left in the custody of his older cousin Jae. Whenever Hyeon gets in trouble with the school's administration, Jae has to be the one to deal with it.
- In Bliss Stage, the Authority Figure is literally the only person over 18 still conscious. Since they usually manage to stay awake through a combination of "drugs, stress, and mental illness," they're not the ideal parents.
- In the backstory of Warhammer 40,000, after the Emperor's incarceration in the Golden Throne, his son Roboute Guilliman was essentially promoted to be the new Emperor until Guilliman himself was mortally wounded. Guilliman also assumed the role the Emperor had to the other Primarchs, attempting to tell them how to behave, how to lead their legions, and what to do in general, though he was arguably unsuccessful in this latter role.
- In Dead End, Drina has been struggling to raise her younger brother Tommy and keep him out of trouble since their mother died. She still dresses like a little girl, despite being in her early twenties.
- In The Most Happy Fella, Marie has been mothering Tony, who is her older brother and now middle-aged, since their real mother died back in The Old Country. She even tries to exercise a sort of Parental Marriage Veto, but she can't stop Tony from marrying Rosabella.
- Nine Hours, Nine Persons, Nine Doors: Santa or Aoi Kurashiki was promoted to parent after his parents were killed in an accident. He's been looking out for Akane since he was 8. It's basically the reason he's The Lancer to Akane when she's acting as Zero - he knows that if her plans fail or never come to fruition then she'll die.
- In Corpse Party, Seiko Shinohara's mother disappeared several years ago. As a result, she acts like a surrogate mother to her three younger siblings while their father works. After Seiko dies in Tenjin Elementary and is erased from existence, her younger brother Yuu is this instead.
- Happens in Crescendo, with Ayame Sasaki taking care of her adopted younger brother Ryo (the male lead) after their parents die in an accident when Ryo was in junior high and Ayame was in college. She drops from college and becomes an Office Lady to support them both, taking care of Ryo devotedly and neglecting her own needs. They can potentially fall in love.
- In the Katawa Shoujo, the lawyer Akira Satou was this to her blind sister Lilly after their parents moved to Scotland and left them behind until the demands of her job force Lilly to start living on-campus at Yamaku. She's quite bitter toward her parents leaving her with Lilly, and thinks she didn't do as good of a job as she could, as Lilly ended up learning how to be independent.
Akira: ...Expecting a nineteen-year-old to be a mother for a blind child. It's ridiculous.
- Phoenix Wright: Ace Attorney:
- Chief Prosecutor Lana Skye, who has been taking care of her teenage sister Ema (13 years younger than her) since the two of them were orphaned. Of course, it's Lana's love for her little sister which leads to her being blackmailed by her boss, Damon Gant, into covering up a crime. Ironically, that leads Ema to hire Phoenix.
- Judge Justine Courtney in Investigation 2 adopted her cousin's son after he was orphaned.
- Shall We Date?: Ninja Shadow: Saori's potential boyfriend Ritsu was orphaned at 10 years old and had to take care of his 6-year-old little brother from then on. Then his brother was killed by the Nagasaki Vigilantes for learning their secret identitites, and the deeply hurt Ritsu has come to loathe them for it.
- Mira Kagami in Tokimeki Memorial is revealed to be unable to join clubs because she's the eldest of five children in a poor household, her father died, and she has to help her mother to take care of her much younger brothers. All of the times Mira cancels dates with the Plyer Character? One of the kids is an Ill Boy and she must take care of him. She's good at sewing? She fixes the kids's clothes to help her mom. She doesn't let the Player Character walk her home? She doesn't want anyone to find out she's not the Rich Bitch she pretends to be at school.
- In True Love Junai Monogatari, Ryoko Shimazaki was raised by her older brother Tadaki ever since their parents died when she was a child. He's also her manager, as she's the local Idol Singer; Ryoko notes that Tadaki has dedicated all of his adult life to make her the best idol in Japan, but has become obsessed with her career in the last years. If the MC wants to romance Ryoko, then it's up to him to help her deal with her manager/tutor/brother.
- When their parents died, Sara from Alone in a Crowd was forced to put her life on hold to look after her sister Faith.
- Syphile of Drowtales is ordered by her adopted mother Quain'tana to raise her younger sister Ariel. She proves to be a terrible mother, receiving absolute hatred from Ariel as she grows up, because Syphile is a completely terrible and excessively cruel person, who beats, insults, starves and otherwise abuses Ariel throughout her early childhood. Drow culture in general expects the elder daughters to step up and raise their younger siblings to prove their maturity before starting their own families.
- In Dubious Company, Gary is this to his "little" brother Marty, from what little is known about them. Nonspecific Evil Mage #157675 learned the hard way what kinds of powers Gary gained from the role.
- Jae Gu of Girls of the Wild's became the sole supporter of his two younger siblings after his father died and his mother abandoned them all out of stress. This is not a happy arrangement, as he works desperately to keep his siblings fed and cared for well also still going through school. He absolutely despises his mother for abandoning them and he fears that if she returns his siblings will easily forgive her and accept her back.
- In Homestuck, Dave's Bro plays it straight while John's Dad is simply a Single Parent, with no insight into the rest of their respective families. Later, thanks to a lot of complicated Ectobiology Shenanigans and Weird Time Shit, we learn that Dave's Bro is his biological clone-father, John's Dad is his genetic half-brother and his grandmother is actually his biological clone-mother, and John is unwittingly responsible for cloning both the parents and the kids just before they all got launched throughout time and space to become those very people.
- Emma in Namesake did have her father around after her mother left when she was a child, but she still pretty much raised her younger sister Elaine afterwards.
- Namir Deiter:
- Snickers after Mrs. Namir runs away (although she wasn't exactly June Cleaver to begin with), especially after Twix comes along.
- Also, after Blue runs away, she's found and raised by her half-sister Roxanne.
- Stand Still, Stay Silent: Part of Onni's backstory. The list of charges includes both a younger sister and a younger cousin; the latter was orphaned at the same time as them.
- The basic plot of Step Monster is that, out of desperation to avoid being split up by the child services, Suzette and Mikey Miller recruit Matilda, the monster who lives in Mikey's closet to pretend to be an aunt of theirs to adopt them. Since the alternative for Matilda is to watch them leave and have to go back to living with her parents in the monster world, she agrees. Things develop from there.
- Strays: Meela's backstory —until her brother got killed.
- Vandi, of What Birds Know, is forced to care for her twin baby brothers after their mother goes into a coma after a difficult childbirth. The story makes it very clear that this is what changed her from a carefree girl into the responsible, serious person she's become.
- Wooden Rose: Lillian has been a second mother to Nessa.
- Bunny has been this to Sweetheart and Speckles, Eglantine, and, of course, Madgie. Needless to say, understandably so, she was rather unwilling to take on these responsibilities but, with her younger cousins, she seems not to mind. However, this is because Madgie is a wanted fugitive, while said little cousins are not.
- Similarly, in Toki and Doki's backstory, the former played this role, when their parents died. Later, we have Jinx and Spin playing this role to Toki, especially since they've thawed her out of the block of ice she was frozen in.
- In the toy lines, Barbie has largely Invisible Parents who only exist in books. It's assumed her two younger sisters live with these usually-unseen parents. In Barbie: Life in the Dreamhouse, however, Chelsea and Skipper clearly live with Barbie.
- Brennus: Basil's sister Amy has been taking care of and supporting him since their parent's died. Granted, she pays the bills by being one of the world's most dangerous supervillains, but she still loves her brother.
- DSBT InsaniT: Snake is like this to Bear, Duck, and Balloon since their father is never on-screen. He keeps them from getting into too much trouble.
Bear: Face it, Duck. Without Snake, we'd be all dead.
- RWBY: In Volume 5, Yang says that she basically raised Ruby by herself due to their father Taiyang not being around often after Summer's death. While the show has been vague as to when exactly this happened (sources have implied Ruby was anywhere as young as two to as old as nine), Yang says that Ruby couldn't even talk at the time, which would mean that Yang herself was no more than four when she started. Its unknown how long this situation lasted, as Taiyang seems more normally involved by the time the series started, and there seems to be little to no animosity between he and Yang in their interactions in Vol. 4.
- In Thalia's Musings, twins Apollo and Artemis became this to each other when Zeus took them from their mother. Artemis appointed herself Apollo's legal guardian.