Practically Different Generations in Fan Works.
Crossovers
- In the Altered Destinies Fan Verse, Alison Managi is the daughter of Superman and Wonder Woman. Not only are both her parents extremely long-lived, being a Kryptonian and demi-goddess respectively, but widowers. Because of this, the grandchildren from their first marriages are older than A-ko.
- Child of the Storm:
- Subverted in the case of Alison Carter. She's presented as Peggy Carter's much younger sister; however, she was actually Peggy's daughter - apparently she would have been passed off as her niece, but Peggy's only sibling died before Peggy entered the war. The trope was invoked to avoid people targeting her for the Super Serum in her blood, and the stigma of the era. Aside from an incident with the Red Room in 1953, it worked for over six decades.
- Wanda Maximoff and her half-siblings Pietro Lensherr and Lorna Dane play it straight - Wanda's in her mid-40s when the series starts, for all that she does not look it. Pietro, meanwhile, is a teenager, and Lorna is about 15, making her roughly the same age as Wanda's daughter Hermione.
- Earth-27:
- When Helena Wayne is born, she's 16 years younger than her half-brother Damian and 10 years younger than her half-brother Terry. And that's without including her adoptive siblings, who are all at least 20 years older than her.
- Dana Tan is ten years younger than her older sister Dorothy.
- Cardinal Matthew Glick was 15 years younger than his maternal half-brother Walter Kovacs/Rorschach, and they didn't get to meet before Walter died.
- Eyes on Me:
- Goldie and Maya are nineteen years old (and their younger brother John sixteen) when their sister Petunia is born. Petunia herself is at least a decade or so older than her biological father Ulysses's children with his wife Penelope.
- Much like in his respective canon, William is a much older half-brother to Edward and Alphonse Elric. This results in Ed and Al being much closer in age to many of their niblings.
- Amy is twelve years younger than her maternal half-sister Tiffany.
- Steven and Connie's youngest child Sirius is a decade younger than their triplets Bree, Nova, and Comet.
- Jonah's tutor Theo turns out to be the much younger half-brother of one of Jonah's grandmothers Sapphire. In fact, there is a whopping age difference of twenty-one years between Theo and Sapphire.
- At the end of Be Wherever You Are, Hope and Jonah get a younger sister named Zoey. Zoey is nineteen years younger than them.
- Eric Cartman is sixteen years older than his younger sister Savannah.
- JoJo New Universe:
- Alongside the canon examples of her half-brother Josuke Higashikata (born 1983) and her adopted sister Shizuku (born around 1999), Holy Kujo (born 1942) also has a younger full-brother named George Joestar III (the Series Fic version of Johnny Joestar) who was born in 1959.
- The canon sons of DIO (the youngest two, Rikiel and Ungalo, born in 1988 and the oldest, Giorno Giovanna, born in 1985) have two significantly older brothers. The first is Enya and Dio's son J. Geil, who was an adult during the events of Stardust Crusaders while they were toddlers. The second is their biological half-brother Joseph Joestar (born in 1920), since DIO conceived them while possessing the body of Joseph's father, George Joestar II.
- The Many Dates of Danny Fenton: In the spin-off The Many Kids of Danny Fenton, some of Danny's potential children (at least in the timelines where he has kids through biological means) have fairly big age differences:
- By the time Tabbi Fenton (Danny's daughter through Sabrina Spellman) is 14 and has started her freshman year of high school, her parents are expecting their second child.
- In the timeline where Danny chooses Musa from Winx Club, they end up having a daughter named Matlin and a son named James ("Jimmy" for short), who're eight years apart in age—by the time Matlin's 16 and is about to start her junior year of high school (at Alfea), Danny and Musa (who're now in their 40s) are expecting their third child.
- One Day at a Time: Bruce Wayne's four biological children, due to both being half-siblings and the younger two biologically engineered, having been born years after Bruce's death. Damian Wayne, the eldest of the four, is fifteen years older than his sister Helena, twenty-five years older than his younger brother Terry, and thirty-one years older than his youngest brother Matthew. Thus, despite legally being siblings of the first generation Wayne Family, the three are officially considered members of the second generation with their nieces Carrie Kelley and Penelope Todd, with the former six years older than Helena. The fact that they were raised by Jason Todd who had a Promotion to Parent, the second eldest of Bruce's original five children, only hammers it in.
- In fan writings by A.A. Pessimal, Assassin Johanna Smith-Rhodes is the eldest of five siblings. She left Rimwards Howondaland for Ankh-Morpork at the age of nineteen. One of the things she left behind was her youngest sibling, who at the time wasn't even two years old. Scroll forward by nine years and Johanna is established as an Assassin and a teacher at the Guild school: the latest batch of eleven-year-old new pupils arrives and one is an overseas student from Howondaland: her youngest sibling Mariella. The two sisters spend time together outside School, and Johanna realizes that with a seventeen-year age difference, their relationship is not straightforward sisterhood - it has overtones of mother-daughter.
- In Make a Man Out of You, there's an over thirteen-year age gap between Ping and Yao Er (and an even larger one between Yao Er and his older sister). This gap means that Yao Er doesn't remember Ping after Ping's been gone in the army for ten years. It also means that he doesn't remember when Ping was still living as "Mulan" before he left.
- In the Skyhold Academy Yearbook series, Evvy (the Inquisitor analogue) is twelve years younger than her eldest sibling Fred. Her son Cole is fifteen years older than her daughter Skye, although in this case Cole is adopted.
- By the time Catalina Madrigal is born in Hurricane Catalina
(part of a larger series of fics), her sister Dolores is old enough to have children of her own.
- Us and Them: Ifalna gets pregnant again around the same time that Aeris is expecting her first child. As a result, Aeris' sister Rakael (a.k.a. "Rockie") is actually a week younger than her own son Keter. Aunt and nephew get raised together and become best friends.
- The Raven's Plan: Stevron Frey is jarred at the fact that his half-sister Roslin is young enough to be his granddaughter, wondering if they ever even interacted with each other before the Remembering. They develop a much closer relationship with each other out of necessity as they take it upon themselves to redeem their family's name in the new War for the Dawn.
- A Nuisance Though Thou Art: The Elf Prince Nemolis Drazhar is in his late twenties/early thirties when he meets his younger half-brother Maia, who's barely four years older than Nemolis' eldest child. Nemolis admits the age cap meant he wasn't very interested in Maia at first — contributing to his neglect — and he's acting more as Maia's parent than sibling.
- Dangerverse: Although technically Hermione Granger's elder sister, Gertrude "Danger" Granger is effectively one of her mothers after their blood parents' deaths. Remus and Danger's daughter Abigail is born when Hermione is seventeen, as is Sirius and Letha's son Marcus.
- Eden, by Obsessmuch: The son Lucius Malfoy fathered with Hermione Granger before he died was born when his mother and half-brother, Draco, were around the age of 19.
- Wish Carefully: In an attempt to bolster their numbers (both as a family and for Magical Britain's population overall), Lucius, his son Draco, and grandson Leonidas all sired new children with the women that were kidnapped to be Breeding Slaves as part of an operation to inject some fresh new blood into the Death Eaters' limited gene pool. As a result, the newly-born Malfoys are all drastically younger than their half-siblings.
- The One-Shot Fic The Argument depicts Helga as an unplanned pregnancy because there's a twelve-year age gap between her and her sister Olga. Her parents decided to keep her, but they still neglected Helga while favoring her sister.
- In the Alternate Universe Fic Joestar Family Groupchat Shenanigans, Jonathan and Dio, the oldest Joestar children, are both 35, while the youngest, Josuke, is 15, which is around the same age as Dio's children.
- Kingdom Hearts 3: Final Stand: Glacies, the elder child of Terra and Aqua, is 18 come the sequel Kingdom Hearts 4: New Light, while her younger brother Ignis is a toddler.
- In Baby Boom (Shawna Canon), due to a poorly thought-out akumatization, thousands of women in Paris end up pregnant, and many of them are mothers with teenage daughters but young enough to still be able to have more children. Marinette and Sabine's babies are the same age despite being from different generations (and in fact, since Marinette gives birth first, Sabine has a grandkid that's actually older than her second kid).
- There's More Magic Out There: When the Mystery Gang meets Madame Nessie, AKA the Loch Ness Monster, it turns out she was found and raised by Anarka Couffaine centuries ago. This makes her the older sister to Juleka and Luka by a couple of hundred years.
My Little Pony: Friendship Is Magic
- In Chemistry, Twilight Sparkle is roughly thirteen years younger than her brother Shining Armor. This is due to an incident where Cadance's love magic accidentally led to several pregnancies.
- In Princess Trixie Sparkle, Celestia has kept a huge secret from her younger sister Luna for over a millennium: they have an older sister named Astelle. Astelle was a teenager/young adult prior to Luna's birth and had already run away. When it turned out Astelle had become evil and vengeful, Celestia decided to keep her a secret from Luna.
- In Grief Not Silent, Mikoto Uchiha was twelve years old and already a kunoichi when her younger brother Obito was born.
- Son of the Sannin:
- Among Jiraya and Tsunade's four children, there is a rather large gap between their eldest daughter Shizune and the rest of their children (sixteen between her and Naruto and an additional three for Hagane and Kaida). In fact, Naruto, Hagane, and Kaida are actually closer in age to Shizune's infant children than they are to her. It helps that both Shizune and Naruto are adopted.
- For that matter, Haku is about 15 years older than his foster parents' biological son.
- In the epilogue, Naruto and Hinata have a second daughter named Urara in addition to their two canon children. She's noted to be around a year and a half while her older brother is about to graduate from the academy, making the age gap between them somewhere between 10 and 11 years.
- Persona 5 Adult Confidant AU: In Persona 5, Sae was 6 to 8 years older than Makoto. Here, the college first-year Sae is nearly 20 years younger than her older sister Makoto, who is in her late thirties like the canon Phantom Thieves in this AU.
- A popular theory is that Ash's barely-mentioned father is Professor Oak. In canon, Professor Oak is his rival Gary's grandfather, which would make Gary Ash's nephew despite being the same age as him.
- In Mended, Delia entered a relationship with Oak and became pregnant with Ash shortly after Oak was widowed. Ash's niece May is older than him.
- Yet the Son Was to Come features Mrs. Bennet finally giving birth to a son at the same time her married daughters are having children of their own.
- Shining and Sweet, a Sequel Series to Ma Fille, introduces a second child to the Beaufort-Kaiser family, Paige, who is fifteen years younger than firstborn Katrina.
- Resident Evil: A Brother's Promise: William "BJ" Birkin, the elder brother of Sherry Birkin, is ten years older than her and also her main parental figure as their parents are obsessed with their work at Umbrella.
- The Simpsons: Team L.A.S.H.: Exaggerated. Anastasia Burns’ half-brother Larry is old enough to be her grandfather.
- knight of the dreadfort (the ballad of the red king):
- Domeric Bolton is three years older than his stepmother Walda "Fat Walda" Frey, so any children between her and his father will be this trope. The same holds true for his half-brother Ramsay.
- Reversed with Roose Ryswell being only a couple years older than his nephews Domeric (see above) and Robert.
- Discussed in We're a Miracle: Mariposa notes how strange it feels to become an aunt at eleven. Meteora replies that she should blame the huge age gap between her and Marco for that.
- Queens of Mewni: Fourteen years separate Soupina the Strange from her younger sister Nebula, the Lady of Three Names. It's strongly implied that their mother Skywynne was so mortified at almost getting caught Making Love in All the Wrong Places (specifically, the kitchen) when she conceived Soupina that it took her years to try having sex again.
- Mother Diamond: By the time Pink Diamond takes her form, her older sisters Yellow and Blue are already centuries old and ruling over their own planets.
- In the Human AU fanfic Too Soon, Winona's twins Yvonne and Beatrix are around seventeen years old when their younger sister Piper is born.
- Super Mario Sunshine: A Sprite of Light introduces Aqua, who is 6 years old in comparison to her sisters Peach and Daisy in their early twenties.
- In The Secret, Emma and her younger brother Billy have a gap of seventeen years between them (at the start of the fic she's twenty-one and he's just four). As a result, Emma ends up acting as a parental figure to Billy at times especially after their mother dies, eventually becoming his legal guardian. To further emphasize this, Billy is still a young child when he becomes an uncle to Emma's newborn son.
- Little Fires: Beechfur is already an adult when his mother Mousestep becomes pregnant again. After she dies in childbirth, he takes guardianship of his little sister Goosekit.
