Temporal Abortion

"And this computer thinks it can win by killing the mother of its enemy. Killing him, in effect, before he's even conceived. A sort of retroactive abortion?"

— The Terminator

The Grandfather Paradox is the single most famous problem when it comes to time travel. The idea that going backwards in time to kill your grandfather would prevent you from doing that in the first place. But what if you really hated someone else instead? Well, it's not too uncommon for time travel stories to involve someone trying to use the Grandfather Paradox maliciously.

If you kill someone else's grandpa in the past, they won't be born in the first place. Hell, you don't even have to kill the ancestors to meet your goal. You can just prevent them from conceiving the person you despise by getting them to split up or make sure they never meet in the first place. Counter to the Grandfather Paradox, this one can be used against future people too. Either you can find out two people will meet to make the next baby Hitler and take actions against that. Alternatively, you find out you're part of that couple and bail before it's too late.

Subtrope of Ret-Gone. Potential overlap with Nice Job Breaking It, Herod. Also see The Time Traveller's Dilemma, where fixing some great wrong has the unintended side effect of erasing innocent bystanders from the timeline. Could overlap with Hitler's Time Travel Exemption Act if the person they're trying to prevent from being born is Hitler. See also Temporal Suicide and Killing Your Alternate Self.

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Examples:

Anime & Manga

• Dragon Ball: Upon discovering the cause of the ghost town epidemic, Krillin and Trunks travel to Dr. Gero's lab to find a solution. During their investigation, they find a sub lab containing the embryo of Cell. The rules of time travel in Dragon Ball mean that killing it then and there didn't kill Cell in the present, but it does prevent the prime timeline from having its own Cell show up in the future.

Comic Books

• One Astro City story features a man who is haunted by the memory of a woman he does not recall meeting, even though he remembers countless details about her. Unable to sleep because of his dreams about her, he finally consults the supernatural being called the Hanged Man, who tells him that the mystery woman was his wife. Thanks to some time-travel shenanigans, history was altered, and she was never born in the present timeline.
• Booster Gold: In the comics' second run, time-travelling hero Rip Hunter states that he is using an alias precisely to avoid the outcome of one of his enemies travelling back in time and preventing his birth.
• In Justice Society of America, Per Degaton once went back in time and killed Rex Tyler's best friend in his crib, just so that Rex would have a lonely childhood.

Comic Strips

• Dilbert: In one comic, Dilbert describes to the Pointy-Haired Boss how the deadline for an assignment is blatantly impossible — so instead, he's going to focus all his efforts on inventing a time machine. The PHB assumes Dilbert intends to use the time machine to go back and finish the assignment on time, but Dilbert corrects him: he's actually planning to find the PHB's parents in the past and educate them on the proper use of contraceptives.

Films — Animation

• Meet the Robinsons: After discovering the horrific, dystopian future that would arrive from the inception of Doris, Louis makes sure to never create her in the first place.
• Shrek Forever After: Shrek makes a deal with Rumpelstiltskin to give him 24 hours to be a proper ogre again in exchange for 1 previous day of his life. Unfortunately, this was a scam because Rumpel actually despises Shrek. The day he took was the day Shrek was born, meaning he doesn't exist anymore, leading to a Butterfly Effect that makes Rumpel the supreme dictator over Far Far Away.

Films — Live-Action

• The Butterfly Effect: In the director's cut ending, Evan time travels into himself as a fetus and strangles himself with his own umbilical cord (and it's implied that this happens every time his parents conceive a son).
• The Terminator: Probably the Trope Codifier. The goal of the T-800 is to kill Sarah Connor before she can give birth to her son John, who will eventually lead the resistance against the genocidal AI known as Skynet.
• Time Cop uses this to explain The Mob Boss Is Scarier. The worst the judicial system is willing to do to you is execute you, whereas the mob boss will have you erased from existence.

Literature

• Animorphs: One timeline where a time traveling Controller's meddling has turned the US into a dystopia so bad the Yeerks have nearly taken over is resolved by asking the freed host where his parents met. He realizes they're asking to Ret-Gone him, but accepts his fate rather quickly (other attempts at changing the timeline for the better are discussed but thrown out since in the current timeline Nazi Germany doesn't exist, but there's still a war between the US and a French-German alliance).
• The First Fifteen Lives of Harry August: As the Kalachakra all possess Born-Again Immortality by way of a "Groundhog Day" Loop, the only way of killing one of them permanently is for an older Kalachakra to prevent the target's birth in their next life, most commonly by feeding abortifacients to the mother during pregnancy — or just flat-out murdering her. Vincent Rankin uses this method to decimate the ranks of the Cronus Club before they can stop him from enacting his apocalyptic plan; for good measure, the fact that nobody knows his date or place of birth prevents anyone from enacting the same trick on him. However, after spending multiple lifetimes pretending to be Vincent's brainwashed comrade, Harry August is finally able to trick him into admitting to when and where he was born, and the book ends with a "fuck you" note from Harry to Vincent as he sets off to erase his Evil Former Friend from existence.
• In Goosebumps: The Cuckoo Clock of Doom, the protagonist winds up doing this by accident. Vandalizing the cuckoo clock results in Michael mentally time traveling backwards. Every time he goes to sleep, he wakes up further in the past, reliving the various ways that his sociopathic younger sister Tara made his life miserable. He manages to reverse the effect just before he has to find out what happens if he travels back before his own birth—but by this point he's already traveled to a few years before Tara was born. Michael wakes back up in the present day, but now he's an only child and nobody besides him remembers Tara at all. Turns out Michael accidentally knocked Tara's birth year off the clock's year dial, so restoring the normal flow of time resulted in a new timeline where she was never born. Michael isn't particularly upset by this.
• In "The Men Who Murdered Mohammed" by Alfred Bester, a scientist attempts to erase his wife's lover from existence by travelling back in time and killing the man's grandfather before his father was born. Despite successfully killing the grandfather in the past when he returns to the present his wife's lover still exists unchanged. The scientist then attempts to change the past by killing history figures of greater and greater importance. In the end he only succeeds in erasing himself from history.
• Sonic the Hedgehog in the Fourth Dimension: After Robotnik gets his hands on a time machine, he starts eliminating all the heroes from existence by sending his robots back in time to kill their parents before they were born. He runs into trouble when he tries to do this to Sonic and Tails themselves, however, as they're both orphans whose real parents are unknown, so he has to send them back into prehistory to kill the first hedgehog and fox ever to evolve on Mobius (and then foolishly tells them about this, giving them the chance to go back themselves and save their ancestors).
• Defied in Desmond Wurzel's short story "Wikihistory". The International Association of Time Travelers has a whole list of historical figures (including, naturally enough, Adolf Hitler) who time-travelers are forbidden from going back and assassinating, because doing so would prevent the invention of time travel itself. Recognizing that time travelers could bypass these rules by assassinating one of these figures' ancestors instead, the IATT passed Bylaw 7 to close off that particular loophole, explicitly forbidding any interference with the ancestors of protected historical figures.
  Silverfox316: Jason440953, see Bylaw 7, which states that all IATT rulings regarding historical persons apply to ancestors as well. I post this for the benefit of others, as I already made this clear to young Jason in person as I was dragging him back from 1875 by his hair. Got that? No ancestors. (Though if anyone were to go back to, say, Moline, Illinois, in, say, 2080 or so, and intercede to prevent Jason440953?s conception, I could be persuaded to look the other way.)

Live-Action TV

• Kamen Rider Kiva: After being driven to the Despair Event Horizon after Mio's death, Wataru decides to go back to the past to prevent his parents Otoya and Maya from ever meeting and therefore preventing himself from being born. He's later dissuaded from doing it, but not before bonding with his father in the past.
• Once Upon a Time: In the third season, the ultimate goal of Zelena (the Wicked Witch of the West) is to open a time portal and alter history so her mother wouldn't abandon her, which in turn would lead to both Snow White and Zelena's sister Regina never being born.
• An episode of Timeless has Wyatt go back to prevent the birth of the man who killed his wife Jessica. It turns out the killer was conceived in a one-night stand and he just has to prevent that. He manages to prevent the killer from being born but Jessica still dies even though the killer's other victims are now alive.
• The Umbrella Academy (2019): After going back in time to the 1960s and returning to the present, the Hargreeves siblings find that they were never born in the new timeline because Harlan killed all of their mothers on the day they were meant to give birth to them.

Video Games

• Command & Conquer: Red Alert 3: In the Empire campaign, the Emperor and his son, Tatsu, learn from Dr. Zelinsky through their android spy that the war was the result of the Soviet Union using time travel to change history. After fending off a joint attack from the Allies and the Soviets on the main islands, Tatsu orders the Shogun to attack Moscow and destroy the Soviet Time Machine, warning that if they change history again, they could end their lives before they are even born.
• In Mortal Kombat 11, Present Kano threatens to do this to Cassie Cage by killing Past Johnny Cage. Unfortunately for Present Kano, Sonya short-circuits this by putting a bullet into the head of Past Kano, which has the effect of killing both Kanos in one move.
• Tales of Destiny 2: Barbatos Goetia develops a deep, seething hatred towards Kyle that leads to him eventually plotting to go back in time and kill his parents before he's conceived.

Webcomics

• Swords: The Time Knife lets the wielder retroactively kill a target without even time-traveling. Unfortunately, as the assassin finds out, it also prevents the client from paying them as they no longer remember the victim.
  Alt Text: Always get paid before you create a paradox.
• VG Cats: In strip #259: The Comedian, Aeris has enough of Leo's stupidity and goes back in time to give his mother, Penny, an abortion with a coat hanger. However he's back to normal on the next page.

Western Animation

• Adventure Time: Upon meeting Prismo and learning of his amazing wish granting abilities, Finn wishes that the Lich "Never even existed." Turns out that the Lich was born from the byproduct of a Nuclear detonation, and undoing him also meant undoing the entire Great Mushroom War, drastically changing the course of history. Alternate Finn unfortunately ends up creating the Lich in his world anyway, and Jake has to exploit the rules of Prismo's wishes to save the world.
• Adventures of Sonic the Hedgehog: In "Robotnik's Pyramid Scheme", the third part of the "Quest For the Chaos Emeralds" saga, Dr. Robotnik travels back in time to Ancient Mobegypt and plots to erase Sonic's family history by ensuring that Sonic's Ancient Egyptian ancestor, Masonic, never meets Penelope, his future bride. He nearly succeeds when Sonic, who followed him through time to stop him causes Masonic to lose his patience at Penelope's chili dog stand, resulting in Sonic disappearing. It takes Tails to play matchmaker for Masonic and Penelope to get Sonic to return.
• Played with in The Amazing World of Gumball. Rob uses a reality warping TV remote to ruin Gumball's life, and Gumball is given a chance to prevent Rob's plan with advanced knowledge of what he'll do to him. When Rob tries to eject his parents from existence, Gumball tackles him to prevent it, only to accidentally reverse their age and turn them into babies. And since his parents are literally at previous points in their lives, they have not yet reached the point where they've given birth to their children, meaning they start fading from existence.
• Archie's Weird Mysteries: In "Alternative Riverdales" following changing history to ruin Archie's life, this turns out to be the final stage of old Vinnie Wells revenge plan. Even despite having already succeeded in making Archie the most hated person in Riverdale and his younger self its God-Emperor, Vinnie is so full of hatred that nothing short of wiping Archie from existence will satisfy him. Thus he attempts to disrupt Archie's parents first meeting so he'll never be born. His actions only succeeding in wiping himself from history.
• Family Guy:
  • Stewie's evil half-brother Bertram attempts this upon discovering Stewie has a functioning time machine. He travels to the late 15th century to kill Stewie's ancestor Leonardo da Vinci. The plan would've worked and caused a universe destroying paradox if not for Stewie inseminating Leo's girlfriend with his own DNA.
  • Stewie intentionally does this to himself after Peter destroys the TV as he's trying to watch his favorite show. He subtly manipulates things so that Peter and Lois split up before he's born, causing his soul to be reborn to a rich British family.
• The Grim Adventures of Billy & Mandy: Exaggerated in "Billy Gets an A". Grim magically changes Billy's test result, but accidentally breaks the balance of the universe in the process, so he decides to travel to the past and fix his mistake. After a succession of failures, Grim resorts to traveling further and further back in time, first trying to prevent Billy from being conceived, then his parents from getting married, then human race from evolving.
• South Park: Cartman doesn't want to go through with the time travel plan in "Post COVID: The Return of COVID" because he loves his life and family in the future. He recognizes that if things played out differently, his children might not exist anymore. Unfortunately for Cartman, his suspicions turned out to be true.