It Runs in the Family. It, in this case, being suicide.
This trope covers instances in which multiple members of the same family commit suicide. In Real Life, many mental illnesses which cause suicidal ideation are known to have a genetic component, making this a tragic example of Truth in Television. However, in fiction, genetics are not typically offered as the primary reason why multiple family members kill themselves.
Frequently, there's a more generalised sense of In the Blood. Or if you want to show that characters come from a Big, Screwed-Up Family or that they are afflicted by Villainous Lineage, Abusive Parents, or a Hereditary Curse, the quickest way may be to give them a tragic backstory that involves multiple members of their family dying by suicide. Or maybe your protagonist fears they will Turn Out Like His Father by being Driven to Suicide. As a result, there's no demand for this trope to apply to blood relatives only. Step-relatives and adoptees can count for this trope, as it just depends on the implications of the frequency of suicide in a family.
This doesn't necessarily require the characters in question to die. It can involve an Interrupted Suicide, and the most optimistic outcome will be a Happily Failed Suicide. Contrast Pater Familicide, which is a murder that often ends in suicide.
As a Death Trope, all spoilers will be unmarked.
- Mars (1996): Rei's twin brother Sei and mother Shoko are Posthumous Characters and we learn during the story that they killed themselves at different points. The story goes to great lengths in showing that both Sei and Shoko were not quite right mentally, with Sei being The Sociopath and Shoko being a Yandere version of My Beloved Smother who had tried to kill both Sei and Rei when she was told she was going to be institutionalized, and thus separated from them. Since Rei's own struggles with his mental health are a major theme of the story, it is heavily implied that these tendencies run in the family.
- Moriarty the Patriot: Both William and his adoptive older brother Albert have had strong suicidal ideation and attempted to end their lives, although neither have gone through with it.
- Neon Genesis Evangelion: When she was a child, Asuka's mother killed herself, and Asuka is the first to find her hanging corpse. Towards the end of the show, Asuka loses her battle against the Angel, Arael, and gets her mind being raped by it. The following episode shows her completely messed up that she tries to kill herself when the NERV personnel finds her in her bathtub with water that looks like it's stained red. Because of this, she has to be put into medical attention with her position as Unit-02's pilot given to Kaworu.
- Cookie's Fortune: At the beginning of the film, Camille discovers that her aunt Jewel Mae or "Cookie" has committed suicide, believing that "only crazy people commit suicide" she tries to cover it up and frame a black man for murder. Only for her cover-up attempts to implicate her as the murderer instead, ending with her hanging herself in jail.
- A Cure for Wellness: Lockhart's father jumped off a bridge to his death after being framed for financial irregularities within the company. When Lockhart starts having trouble at work that requires him to go to the remote Swiss spa, he becomes increasingly worried about the trope happening to him, too.
- The Game (1997): Nicholas fears this trope, shaped by his childhood memory of seeing his father commit suicide by jumping off the roof of their family home. The game's organizers seem to exploit this fear and try to gaslight him into doing the same; at one point Nicholas finds a police photo of his father's body captioned "LIKE MY FATHER BEFORE ME I CHOOSE ETERNAL SLEEP."
- The Handmaiden: Subverted twice. Hideko's aunt apparently hanged herself due to her uncle's horrific abuses, and Hideko keeps a rope to hand to be able to kill herself if the abuse should become too much. However, Hideko's aunt's suicide turns out to have been feigned by her uncle, who actually killed her himself. Although Hideko does jump from the tree ready to kill herself at one point, Sook-hee catches her and holds onto her to prevent her from doing so. It ultimately becomes a Happily Failed Suicide.
- Hereditary: Annie's father starved himself to death, her brother, Charles, hanged himself, and Annie doused herself and her children Peter and Charlie in paint thinner and was about to set them alight. In her sleep. This turns out to be because of a curse on their family, which ultimately comes true when Annie (possessed by the demon Paimon) saws off her own head with razor wire and Peter is overcome by grief and jumps to his death out of a window. Too bad for him that that's actually what the cult wanted all along, and he survives, albeit possessed by Paimon/Charlie.
- La piel que habito: Robert's wife jumped out of a window to her death after seeing her badly-disfigured face. Her daughter with Robert, Norma, was badly traumatised by witnessing it. After Vincente tried to rape her, Norma finally became so unstable that she killed herself in the same way.
- Last Night in Soho: Eloise's mother committed suicide when she was a child, and Eloise fears the same thing happening to her as she undergoes Sanity Slippage. Thankfully it doesn't.
- Oldboy (2003) has an unusual variation by the way of Together in Death due to the role of BrotherSister Incest. Soo-ah commits suicide by jumping off a bridge after she believes that she's pregnant with (her brother) Woo-jin's baby. After Woo-jin exacts his revenge on Dae-su decades later, he shoots himself.
- A Simple Plan: Jacob reveals to Hank that the drunken accident that killed their father was actually a suicide, in a desperate attempt to get money for Hank's education. After their plan for the money unravels, Jacob can't live with himself and tells Hank that he'll kill himself and implicate everybody in the theft unless Hank kills him instead. So Hank does that.
- The Skeleton Twins: The Movie. Milo and Maggie's father died by suicide after jumping off a bridge. The movie begins with Milo and Maggie both separately attempting suicide (he with a Bath Suicide, she with Suicide by Pills). It then ends with Milo saving Maggie after she attempts suicide a second time, which leads them both on some sort of path, it seems, towards working out their issues.
- Wristcutters: A Love Story: Eugene and his entire immediate family - mother, father, sibling - all committed suicide and live together in suicide land.
- Father Brown: In "The Doom of the Darnaways", there's a legend that every seventh generation in the Darnaway family, the heir will die by suicide. Subverted - the legend was invented to make people suspect suicide rather than murder when the next heir dies.
- In Fire & Blood, both Helaena Targaryen and her daughter Jaehaera end up committing suicide by throwing themselves from Maegor's Holdfast into the moat (unless you go with the unproven rumor they were pushed). Both had suffered depression and mental instability after going through severe trauma, possibly stemming from the same event: they both witnessed the murder of Jaehaerys, Helaena's eldest son and Jaehaera's twin brother. The fact that the Targaryens were known for incestuous marriages, with Helaena's own children being fathered by her brother, may not have helped due to possible genetic defects.
- In the backstory of Norwegian Wood, Naoko's older sister hanged herself as a teenager. Naoko ultimately goes the same way.
- Discussed in Sparkling Cyanide. The initial plan of the murderers is to make Iris Marle's death look like suicide so that the police would think suicide runs in the family, as the murder of Iris's sister took place the previous year on the exact same day and successfully passed off as suicide. Due to a Spanner in the Works, however, the plan fails and another person gets murdered, whose death is clearly not a suicide.
- The Virgin Suicides: A couple of months after Cecilia's suicide, all four of the other Lisbon girls, her sisters, die by suicide (in the film, Mary dies in the mass suicide, whereas in the book, she actually survives that attempt only to overdose on pills and die later.)
- In God Bless You Mr. Rosewater by Kurt Vonnegut, Fred Rosewater's father committed suicide. Fred often thinks about killing himself and once nearly goes through with it, but gets interrupted.
- Cold Case: Invoked/Played With in one episode. The team reopens a woman's apparent suicide when her suicide note is found and doesn't match her handwriting. Over the course of the investigation, they learn that the woman had recently discovered her own mother had hanged herself, rather than Death by Childbirth as she had believed, and was exhibiting signs of the same mental illness shortly before her death. Turns out her husband had learned about the mother's suicide and was gaslighting his wife so she'd seem to be following in her mother's footsteps. Whether he was hoping to drive her to suicide or just discredit her so she wouldn't notice he was stealing her poetry, it didn't work, so he killed her to keep her quiet.
- Criminal Minds: One unsub abducted his daughternote and recreated a road trip he'd taken with his father when he was a child. The team then learns that the father had committed suicide at the end of this trip and written his suicide note on a series of postcards, and the unsub has made a point of getting postcards at his stops. JJ, who lost her older sister to suicide, convinces the unsub to break the cycle by not letting his daughter watch and/or see him dead. When his daughter figures this all out, she manages to convince him not to go through with it at all, convincing him life is still worth living even if he's in jail, because they'll still be able to have contact and he'll get out eventually.
- Desperate Housewives: In "Nice She Ain't", Danielle attempts a half-hearted suicide by smashing a beer bottle on her own head, taking pills, and slashing her wrist with a spoon. When her brother Andrew laughs this off as a cry for attention, his stepfather Orson snaps at him for making light of suicide. While it is initially believed that Orson's own father had committed suicide, it is ultimately revealed that his mother Gloria killed him as revenge for cheating on her.
- Dexter: The Mitchells have this going on, both due to extreme bad luck and, in the present, Arthur/Trinity's horrific abuse. Arthur's mother committed suicide by jumping off a rooftop after his sister died falling through a shower, two actions that got Arthur on his Start of Darkness. Arthur's daughter by a previous relationship, Christine, then Ate Her Gun in Season 4 because Arthur rejected her after she killed Lundy for him. Sometime before Season 6, even after Arthur's own death, his wife Sally drove their daughter Rebecca to suicide with constant verbal abuse.
- During the backstory to The Haunting of Hill House, Olivia Crain committed suicide after being left alone in the eponymous Haunted House; by the end of the first episode, her youngest daughter Nell apparently does the same, hanging herself from the very same landing that Liv jumped from. When Nell's twin brother Luke goes missing following the funeral, Theo is immediately concerned that he might be planning to commit suicide as well - though he's actually set out to burn down Hill House. Plus, despite Steve's obsessive belief in the family's inherited mental illness, it turns out that the "suicides" were due to the House's influence.
- Nine Perfect Strangers: Napoleon and Heather's son Zach committed suicide. In an Adaptational Angst Upgrade, Heather contemplates jumping off a cliff in the run-up to Zach and Zoe's birthday, but she doesn't go through with it.
- The Pact: Louie and Arwel's father hanged himself twenty-five years ago, apparently because he couldn't bear the guilt of having abused Arwel when he was younger. Arwel then committed suicide after his own son Jack's murder, either because the grief was too much or because he had also gone on to abuse Jack.
- Veronica Mars: Lynn Echolls throws herself from a bridge when her husband Aaron's adultery and physical abuse becomes too much for her. Her son Logan is about to jump off in the same place at the end of Season 1 when he gets jumped by the PCHers, and Felix is murdered.
- Jocasta hangs herself in Oedipus the King when she learns that she had sex with her son. Their daughter Antigone then also hangs herself in Antigone.
- Antigone's suicide in Antigone also sets off its own chain. Her husband-to-be (and cousin, and adopted sibling), Haemon, stabbed himself after finding out that Creon was too late to save Antigone. Haemon's mother, Creon's wife, then stabbed herself upon finding out about her son's death.
- In Fatal Frame, both Miyuki Hinasaki and her grandmother Yae Kurosawa committed suicide many years apart due to issues with malevolent ghosts haunting them.
- Implied in Paranoiac. It's revealed that Miki's maternal aunt Saeki committed suicide (with Miki being the one to find her body) after suffering from severe depression and a delusional disorder. Miki herself has depression and is diagnosed with schizophrenia in the good ending. In the bad ending, Miki is seemingly killed by the monster that has stalked her throughout the game but given the suggestion the monster is all in Miki's head, she may actually have killed herself (the remake adds credence to this by stating her death was officially ruled a suicide). It's indicated that mental illness runs in the Takamura family as Miki, Aunt Saeki and Miki's mother all struggle with disorders and past trauma. Of course, this is dependant on which ending you get as in the good ending Miki survives and starts getting better.