Gumball: So, you mean love multiplies?
Nicole: No, it divides. But I'll take the difference from your dad's portion and hope our marriage survives until you go to college.
Richard: Mm-hmm... wait, what?
In stories aimed at children in particular, it is a common plot for the child characters to dislike it when their parents have a new child. Reasons for this differ from being jealous of all the attention the new baby is getting, being worried about falling into Middle Child Syndrome, or disliking how noisy and messy babies are.
Rarely however does this train of thought last past early childhood, though. The dynamic almost never becomes of the Cain and Abel sort once they're older, though a Sibling Rivalry is common. The character might end up with shades of a Big Brother Bully but overall they are shown to love their sibling. There is frequently an aesop where the kid learns to love their sibling, or simply they grow out of it.
Compare to Dislikes the New Guy.
- One car commercial features a little girl who likes having everything her way and to herself, such as her parent's car. She doesn't take it well to the news that she'll soon be an older sister.
- Fullmetal Alchemist: In a manga-only short, it's shown that Edward disliked Alphonse when they were infants. As a toddler, Ed thought their mother loved the baby more than him. It wasn't until his father told him otherwise that Ed became the very caring brother we know today.
- Kun in Mirai of the Future quickly notices how his parents are paying more attention to his newborn sister than him, complete with 4-year-old tantrums about it. By the end of the movie, he comes to terms with having Mirai in his life and develops a proper Big Brother Instinct.
- Played with in My Next Life as a Villainess: All Routes Lead to Doom!, given that the younger sibling is adopted and there's only a few months between them. The original Katarina from the game was incredibly jealous of Keith stealing away their father's attention and would verbally abuse him well into their teenage years (something that leads to her death in at least one of the routes). The new Katarina (having the Past-Life Memories of a Japanese schoolgirl who played the game and always wanted a younger sibling) defies this and tries to be his Cool Big Sis almost immediately after meeting him.
- For Better or for Worse has young Michael learn to dislike his younger sister Elizabeth, who tends to be invasive and a crybaby. Not helping is that their mother, Ellie, tends to side with her in most disputes. Mike even has a nickname for Elizabeth: E. Lizard Breath. They grow out of it, especially when the newest rugrat April arrives.
- Baby Blues has older sister Zoe dismayed that her infant brother Hammie has taken away much of her face time with her parents. Wanda, of course, must be more careful with the infant, while Darryl no longer focuses solely on his "little princess," rather he marvels at having a son, a "chip off the ol' block." The antagonism eases once Wren is born.
- In Rerun's introductory story arc in Peanuts, Lucy is shocked to find out from her mother that another little brother has been born when she just kicked Linus out of their house. Linus isn't fond of Rerun at first, because Rerun will not stop crying when all he wants to do is read his book. Lucy tells Linus that she went through a similar experience with him when he was a baby, which inspires Linus to name their little brother Rerun. Lucy originally wondered why she couldn't just be an only child, but as time went on, exposure to Rerun began to affect her in a positive way.
- In the oneshot Her Max, Ruby initially didn't like having a sibling. She liked being the center of her parents attention. Quickly, however, Ruby began to like taking care of Max and being a big sister.
- Initially, fifteen year old Ash doesn't like the idea of having a new half-sibling in Empty Nest. It isn't until Misty notes that he'll be able to teach his sibling about Pokémon that Ash starts liking the idea of being a big brother.
- The Code Geass oneshot Lesson One is about Cornelia telling a toddler-aged Lelouch how to be a good older sibling to his new sister Nunnally. Lelouch doesn't like Nunnally because he's afraid she'll get all the attention.
- Twelve-year-old Dick Grayson doesn't take graciously the apparition of toddler Damian into his and Bruce's life into In For a Penny, eagerly waiting for Bruce to send the baby back to his mother. He ultimately confesses his fear that Bruce will stop to care for him with his "true", biological son at home.
- Destiny: Lady ran away from home because her parents were having a baby and she was worried that her parents wouldn't love her anymore. Lady trusted the wrong man and was killed by him.
- In The Rugrats Movie, Tommy doesn't get along with his newborn brother Dil at first. He hates how much noise Dil makes and feels his parents are neglecting him to focus on his brother. Tommy and his friends trying to send Dil back to the hospital is how they end up lost in a forest. By the end of the film Tommy realizes how much he loves Dil and his Big Brother Instinct often appears in later episodes of the TV series. This is possibly the only example of this trope where the older sibling is a baby too, only a year older than the newborn.
- In The Boss Baby, Tim is envious of the attention his baby brother receives, and suspicious when the infant acts odd around him. Tim soon finds out that Boss Baby is on a mission to discover why babies are losing their market share of love, and originally agrees to help him for the sole purpose of wanting him out of his life. Over the course of the movie, Tim and Boss Baby bond with each other, and by the end, when they finally achieve their goals, they realize how much they miss each other and agree to officially become brothers.
- Dingo Pictures: In an infamous scene from Dinosaur Adventure (that was the origin of the "Yee" meme), Tio finds out that he has a new brother and is worried that his parents don't want him anymore. His friend Peek teases him about it.
Peek: Mom and dad have a new baby, now you are nothing for them.Oro: Yee ("Peek!" in the original version). How can you say something like that, the majority of us have brothers and sisters, the parents love all their children in the same way.
- A large part of the plot of the first Franklin movie, Franklin and the Green Knight, is Franklin worrying that he'll become The Unfavorite when his new baby sister is born. This worry is only increased when everyone fawns over the upcoming baby during a baby shower. Later, this fear is soothed when he meets an armadillo with a baby brother who tells him that his parents have enough love for both him and his brother. Franklin's friend Snail has a similar fear - he worries that Franklin won't have any time for him once the baby is born. Oh, and Franklin's worries being soothed turns out to be reasonable, as there is no evidence in the fifth and sixth seasons of the show (both of which feature a version of Franklin's new sister, Harriet, that is able to talk and walk), that either child is treated as a favorite.
- Zig-zagged in Stuart Little. Stuart's brother is happy that his parents are adopting a kid, however he is upset when his new sibling turns out to be an anthropomorphic mouse. He takes some time to warm up to Stuart.
- The Little Rascals episode "Bouncing Babies" has Wheezer get a baby sister that cries and fusses too much. Wheezer's friend Farina suggests taking the infant to the hospital and trade it in for a goat, which is precisely what Wheezer does. After learning an important Aesop, Wheezer undoes the exchange.
- In Addams Family Values, Wednesday and Pugsley believe that, in the Addams Family, when a new child is born, one of the old children has to die, which simply isn't true (well, not anymore). Despite this, they spend a lot of time seemingly trying to murder their new baby brother. Then again, this being the Addams family, that may just be how they show affection.
- Sherlock Holmes: In "The Sussex Vampire", Holmes investigates claims of a man's wife sucking the blood from her own newborn's neck. The real culprit was the man's first son Jack, who hated his stepbrother for the attention it was taking away from him, and for not being deformed like he was. The mother was sucking out the poison from the blowgun darts Jack had used to try to murder the baby.
- In The Berenstain Bears and Baby Makes Five, Honey Bear is born, and Mama, Papa, and Brother spend all of their time with her, making Sister feel largely ignored. Sister also becomes bad-tempered, to the point where when she had a school assignment to draw a picture of her family, she deliberately left Honey out of the picture. The Bear family then shows Sister home movies of when she was a baby, which makes her realize that she used to be just like Honey. This causes Sister to change her attitude towards Honey, to the point of drawing a new family picture that includes her.
- In Julius, the Baby of the World, Lily was originally thrilled to be a big sister when her Mom was pregnant with her baby brother, Julius. Following Julius' birth, she took on a more hostile personality towards him. She did not like having to share her bedroom with him, and hoped her parents would send him away. She even tried scaring him, making him disappear, and pretending he didn't exist, all of which sent her to the uncooperative chair. When Lily's parents throw a party in Julius' honor, Lily's cousin Garland acts the same way towards Julius that Lily did, which causes Lily to change her attitude towards Julius for good and defend him.
- It's mentioned off-hand in A Series of Unfortunate Events that Klaus disliked Sunny at first. He grew to like her within 6 weeks of her birth.
- In the book Stupid Baby, the bunny Simon gets a brother who he thinks is stupid.
- Averted in Junie B. Jones. When the titular character is told by her mother that she will be having a baby boy, she is overjoyed. She also thinks about being bossy towards him. When he's born, she actually mistakes him as a monkey and brags about him to her friends.
- In Ramona Forever, when Mrs. Quimby becomes pregnant, Ramona struggles with the thought of losing her status as the youngest and becoming the middle child. When her new sister is born, she feels even more left out when she's not allowed to visit her in the hospital. A friendly doctor diagnoses her with "siblingitis" and "prescribes" some extra attention as the cure, which her father duly gives her.
- Charlie in Good Luck Charlie constantly asked that her baby brother Toby be left somewhere, thrown away, or ignored him as much as she could get a way with. Gabe felt the same way about her, and each older sibling of the Duncan household felt the same way about their immediate younger sibling.
- The Fresh Prince of Bel-Air: This is Ashley's subplot in the episode where the family thinks about how the new baby will impact their lives. She has a fantasy about the entire family ignoring her and even forgetting her name, as she will no longer be The Baby of the Bunch.
- On Charmed, toddler Wyatt winds up getting so jealous of baby Chris that he keeps using magic to steal his stuff, and eventually orbs him somewhere outside the house, where he's thankfully found by Victor. Grams casts a spell that is supposed to end their sibling rivalry, but it backfires by making the sisters act like immature children instead.
- In The Sims 4, while it is possible for them to be happy about it, there are also two potential negative moodlets that children and teens can get from meeting a new sibling. There's a sad "New Sibling..." moodlet and an angry "Unwanted Sibling" moodlet.
- In the The Wubbulous World of Dr. Seuss episode, "Lester Leaps In", Sarah Hall-Small becomes jealous of her new little brother, Paul, because of how much time her parents spend with him, and how they hardly pay attention to her anymore. Whenever they do, it's usually to remind her to be considerate of him, such as not playing her big bass thumper bumper too loud when he's trying to sleep. Sarah eventually gets the idea of acting like a baby herself to get her parents' attention, until her parents tell her that they'll always love both her and Paul equally. Upon hearing this, Sarah changes her attitude about Paul and promises him that she'll be the best big sister ever.
- In the Sesame Street 3-part episode, "Three Bears and a New Baby", Baby Bear has mixed feelings about his baby sister, Curly. While he is excited about being a big brother, and even gives Curly her name, he worries that their fairy tale, The Three Bears, will never be the same again. Baby Bear's first night with Curly doesn't go over too well, due to how much attention their parents give her, and this also interferes with his bedtime routine. Papa Bear tells Baby Bear that he will always love both him and Curly equally, and will find a way to have time for them both.
- In the Wimzie's House episode, "Babies Have It Made", Wimzie is jealous of her baby brother, Bo, because he doesn't get scolded for his actions due to not knowing any better, and their parents and grandmother have to do everything for him. This makes Wimzie wish that she were a baby herself during her naptime. Wimzie then has a dream that makes her experience what it's like to be a baby, and she finds out it isn't as fun as she thought it would be, due to her friends and family not understanding her, and having to eat baby food instead of pizza. When she awakens from her dream, she realizes the advantages of being a five-year-old kid and changes her attitude towards Bo, even going as far as defending him when Jonas objects to her hugging him.
- One common type of GoAnimate video is "X calls the Baby Stupid", wherein when a new baby is born or brought home, the older sibling (sometimes an original character, sometimes a character from a show aimed at kids the user really doesn't like) will call the baby stupid. This will cause the baby to cry, and the parents will ground the older sibling for a ridiculously long time, causing them to run away crying. They will then calm the baby down and tell them their older sibling can't bother them anymore.
- Age Of Bronze: Deiphobus really does not like that Paris is revealed to be his long-lost brother, especially after he'd beaten all the royal children (himself included) at the games. That Paris continues to gain honor and glory (and the most beautiful woman in the world), further cementing his place as second in line to the throne (after Hector) doesn't help at all.
- Yet Another Fantasygamer Comic: When it's revealed the baron's son Lucas and the blacksmith's (half-orc) son Glon were Switched at Birth, Lucas does not take it well at all, even if Lucas eventually succeeds the baron and Glon stays in the Black Mountain. Both eventually get much better, and become true Bash Brothers in time.
- Inverted and invoked in The Amazing World of Gumball episode "The Rival", the Whole Episode Flashback to Anais's birth: Gumball and Darwin were looking forward to their new baby sister, but she turns out to be a murderous Brainy Baby who sees them as competition for their parent's affection. Nicole still ends up giving her sons the usual spiel about not loving them less with the new baby, but only because Anais framed them for bullying her.
- A variation occurs in Jem. Flashbacks shows that Jerrica and Kimber disliked their foster sisters, Shana and Aja, when they met as children. They, however, became best friends within a year and by the time they're adults they're in a band together. The series treats them more like friends than sisters, though the comic reboot makes it clear that they're sisters.
- In the Kim Possible episode "Big Bother", Ron's parents adopt a little girl called Hana. Ron is not happy, though at least part of this is because his parents were absurdly sudden about it, only being told once Hana took his room. He gets over it after Monkey Fist attacks her, and adores her for the rest of the series.
- Rugrats: In "Angelica's Worst Nightmare", Angelica freaks out at the news that her mother is pregnant, to the point where she has nightmares about having a baby brother who steals all her stuff, turns into a giant, and eats her. Most of it stems from the fact that Angelica is used to being treated like a princess, and that she doesn't like having to share anything, especially her parents' love. Subverted, however, when it turns out that her mother had false pregnancy symptoms.
- The Simpsons episode "Lisa's First Word" shows Bart was unhappy with Lisa's birth, especially with Homer fawning over her because it coincided with a run of good fortune. Though a good part of Bart's misery came from random events indirectly caused by Lisa (e.g. Lisa gets Bart's old bed, so Homer makes Bart a new one with a Monster Clown carved into the headboard). He was about ready to leave home until hearing Lisa's first word was "Bart".
- In the Arthur episode, "D.W.'s Baby", D.W., who was at first, thrilled to have a new baby sister, quickly grew tired of having Kate around the house, due to her constant crying at night and stinky diapers. She tried to get Kate in trouble by blaming her for things she or somebody else did, and even tried to sell her at a Garage Sale for 50 cents. When she runs away to Grandma Thora's house, Thora reminds D.W. that when Kate grows up, she'll have a mom, dad, and brother, but no sister to take care of her. This quickly convinces D.W. to go back to her house and be the best big sister ever to Kate.
- In the Dinosaur Train episode, "Tank's Baby Brother", Tank the Triceratops gets a new baby brother, Tuck. Tank dislikes all the attention Tuck gets from his friends and family, and feels largely ignored. Buddy and Tiny soon realize how upset Tank feels and decide to play with him to cheer him up. When Tuck says his first word, "Tank", Tank quickly warms up to him.
- In one episode of Caillou, the titular character is not happy to see that his new sister, Rosie, is getting more attention from the family than him. This infamously leads Caillou to pinch Rosie at some point in the episode.