One quick way to establish conflict for a male lead (and it is almost always a guy used in this trope) is to make them a divorced (occasionally separated) father. The story will usually open with a first act divorce or some time after it has taken place, with the children old enough to start resenting their dad for "leaving them". For whatever reason things didn't work out with his Love Interest and they separated, with her usually keeping near complete custody.
For whatever reason, it's always implied it's the dad whose flaw(s) led to the divorce; while the ex may be snarky, resentful or exasperated in their interactions, neither the lead nor usually the children will act as if she was the problem. Still, just as often this makes us sympathise with the father more, if she comes off as seriously insensitive or unforgiving in the course of this.
She will have either remarried, gotten a fiancé or is seriously dating someone else. Since she has custody of the kids, the First Dad will be worried the Step Dad will win them over because he has more time with them and he's handsomer, more successful, more empathetic and an all around better dad (though a painfully dull and "safe" rebound guy is also possible). The kids, usually boy and girl pair, will have one of four relationships with the First Dad and Step Dad: passive aggressiveness, wary distance, civil cohabitation, or a loving and respectful rapport. For variety and contrast, they usually each have a different relationship with the dad and step dad.
There are two variants:
Family-focus variant: The lead thinks they should get back together, which his ex wife will rebuff because "You haven't changed" the underlying character flaws that led to the divorce. As the plot progresses, he'll win back his ex wife, the Step Dad will be revealed to be a Jerkass and get killed off or sent packing, he'll completely patch up his relationship with his kids and they'll all reunite and live Happily Ever After.
Child-focus variant: This variant focuses on the child (and in this case, it's almost always a single child) over the family as a group. The lead and his ex-wife will be relatively civil, with surprisingly little UST (although he'll still needle her over her new significant other, and she may throw some snark his way). In this case the ex wife usually wants to be supportive of the lead, but is seeing the way his character flaw hurts the child. Expect the lead to be given "one last chance" often with the threat of a new job that will take the child to a different city. Of course, the lead blows it, leading his child to think he doesn't love them, before he makes it up to them in some over-the-top fashion and convinces his ex-wife to stay. Either he and the step-father will learn to respect each other and share their role in the child's life, or the step-father will bow out of the way for the good of the child (often leaving for the aforementioned new job).
- Cassie Lang: Cassie greatly adores her father Scott Lang and wants to follow in his footsteps in being a superhero. However, she has a strained relationship with her stepfather Blake Burdick, a police officer who cannot stand the world of superheroes the young girl loves, and he unsuccessfully tries to keep Cassie and Scott apart. In the events of "Avengers Disassembled", when Scott is killed due to the actions of an insane Scarlet Witch, Cassie retreats into herself, blaming Blake for being unable to understand her as her father always did. Though Blake does try unsuccessfully to be a caring stepfather, despite sometimes being distant toward her and seeing her as a "less than brilliant" girl, it is clear that Cassie favors her father over him.
- 2012 mixes it up a bit. Step Dad Gordon is a Nice Guy, saves their lives twice, and has honestly won the love and respect of his kids. Of course, the ex-wife loves him imperfectly, not as much as her old husband who she has a flame for, but enough to not leave him. And of course he dies at the end in what seemingly is a last-moment attack by the plot to keep this trope enforced BY ANY MEANS.
- Ant-Man has Paul Rudd playing the other half of the second variant. Although Scott is more concerned with getting to be in his daughter's life than her affections. While Cassie loves her stepfather Paxton, it's clear that she prefers and favors her biological father.
- Are We There Yet?: Deconstruction. Lindsey and Kevin Kingston greatly adore their divorce father, Frank, and they made it their mission to chase away their mother, Suzanne Kingston, boyfriends until their parents reconnect. It is evident that their mother has no interest in reconnecting with their father. While Suzanne was talking on the phone with Frank, who said he was sick, so he could not pick up their children and spend time with them, she revealed he not spend time with them since Labor Day, and while arguing with her, he just hanged up on her. This implied that Frank has not stayed in contact with his ex-wife and children after the divorce. Lindsey and Kevin run away from Nick Persons there mother's friend. When they learn, Nick is interested in their mother; they decided to go to their father's house, believing they can get their parents to fall in love again. But when they get to their father's house, they see through a window that he not sick, and with a woman and infant implied to be his new wife and child. Lindsey and Kevin realized that their father lies about being sick, so he does not have to see them and cut them from his life. Even Nick, who was understandably angry with them, was sympathetic when he learned this and told them how his father abandoned him and it was not their fault that their father was losing out on having his children in his life. Those painful, Lindsey and Kevin accepted that their father does not want them in his life and accept Nick as their new father figure.
- In Bringing Down the House, the mother's new boyfriend is perfectly nice, but he's a lot younger than her (and her ex-husband.) Presumably the age difference helps her decide to go back to her ex once he becomes less of a workaholic.
- This trope serves as the basis for Daddy's Home: when Dusty discovers how much his children have bonded with their new stepfather Brad, he determines to win them back and force Brad out. Averted at the end, when the two dads come to a mutual understanding... then Dusty gets married and becomes a stepdad himself, upsetting his stepkid's father, Roger.
- Gender swapped and subverted in Definitely, Maybe. A closer look at the movie may suggest that daughter Maya asks her father about how he met her mother to encourage him to rekindle old feelings. But when he tells her about the three major women in his life he realizes that the woman he loves isn't Maya's mother, and Maya then encourages him to follow his heart, even if it doesn't lead her parents to remarry.
- Domestic Disturbance is good example of this trope. The stepfather seems to be a successful businessman, but the son soon discovers that he is actually a killer. In the end, the first father (John Travolta) wins.
- While there's no romantic rival, reuniting with his wife and daughter is William Foster's primary motivation in the movie Falling Down. Foster doesn't just have "frustrating flaws" the way so many First Dads have; he's insane to the point that his own mother is terrified of him, and his ex will do anything to keep away from him. Since it's a drama, it doesn't end well: Foster ends up committing Suicide by Cop.
- The Belgian film Le huitième jour involved this as a major part of the plot.
- The Full Monty has Gaz trying to raise the money so that he can keep seeing his son on weekends. He goes about this by... unconventional means, which backfires when the police see him and his friends practicing their strip tease in front of the kid and arrest him.
- Liar Liar is a fairly straight example of the child-focus variation, with a reliable but boring new father figure who winds up getting the shaft just as she and the ex-wife were about to move away together. Fletcher and Audrey show no real UST both being much more focused on Max's well-being. It zigs back into the family-focus variant during the stinger, which takes place a year after the climax of the movie.
- Mrs. Doubtfire has the example of Robin Williams's character cross-dressing as a nanny to spend time with his kids, while meanwhile Pierce Brosnan's character romances the ex. It leads to his ex-wife gaining full custody and forbidding him any contact with his kids without supervision. Double Subverted when the ex-wife allows the dad to visit the kids anyway and their dad takes the cross-dressing professional with a motivational childrens' show.
- Night at the Museum is the family-focus variant. Ben Stiller's character main motivation is proving himself a worthy father to his son, and to himself, but he and his ex-wife have an almost sibling like relationship, with absolutely no UST and Paul Rudd, the step-dad, is shown as goofy but dedicated and never actively tries to get between Stiller and his son. Which makes him all the bigger threat.
- O Brother, Where Art Thou? has the wife of the protagonist (a convicted felon) attempt to marry a man with an honest living, whose worst fault appears to be that of being boring. Interestingly, the step dad is in the Ku Klux Klan, and gets swept out of the way because of it. The protagonist and wife eventually get sort of back together.
- The Royal Tenenbaums has Royal try this to return in good graces with his family, including getting rid of his ex-wife's suitor by pretending to have stomach cancer. The Step Dad eventually sees through his ruse and they kick him out. They do eventually forgive him though.
- Run, Fat Boy, Run! is quite literally this trope. The real dad does indeed beat the stepdad in the London Marathon, thus winning back the mum.
- Played With in The Santa Clause: it begins with Charlie clearly preferring his stepdad, Neil, to his workaholic father Scott, but Scott becoming Santa Claus helps to bring the two together. This leads to a rift between Charlie and Neil in the latter half of the movie—Neil is convinced Scott is delusional—but ultimately Charlie's relationship with both father figures is repaired. There's never really any hint that Scott and his ex-wife, Laura, might get back together.
- Sharknado is particularly blatant with the Jerkass new boyfriend, but he gets all of two minutes on screen before getting eaten. Makes you wonder why they bothered, unless it was meant to be a subtle parody. Naturally the protagonist and his ex get back together at the end, despite another woman also interested in him. (Who may hook up with the protagonist's son instead.)
- In Taken, Bryan's wife divorced him because of his time-consuming job as a special forces commander. She has remarried a millionaire and has custody of his daughter, Kimmy. Their relationship is summed up at Kimmy's birthday party, when Bryan gives her a karaoke machine, but her stepdad gives her a horse. The trope is ultimately subverted in that even though he regains the respect of his daughter and ex-wife after rescuing his daughter from kidnappers, they don't reunite as a family. Until the sequel.
- Ultraman Cosmos: The First Contact: The movie prequel to the television series have this dynamic between protagonist Musashi Haruno, then an 11-year-old boy, and his stepfather Yujiro Haruno, who is a replacement after Musashi's biological father died in an astronaut mission years ago. For most of the movie Musashi pins after his deceased father, while Yujiro tries his best to show his stepson how much he cared for the boy, but by the end of the film Musashi finally learnt to embrace Yujiro as a father.
- The War of the Worlds with Tom Cruise has this set up, and plays it to a T except for the reunited parents.
- The Weatherman with Nicolas Cage has this set up... which remains largely unchanged by movie's end, save for a slight repair in his relationship with his kids as he works out some personal issues.
- Played painfully straight in The Strain with Matt, who is a cowardly, passive aggressive milquetoast department store manager described as a safe rebound guy. He tries to sabotage Eph's relationship and credibility with ex-wife Kelly, and tries to take Eph's place with son Zack. This in the middle of a
ZombieVampire Apocalypse, which leads to his convincing Kelly that Eph's warnings are a desperate cry for attention, which leads to both being turned into vampires. The trope is played so straight he seems to have a total lack of redeeming features, and when Eph beheads his vampire form, it's a toss up as to whether the feeling is cathartic or not.
- Banshee: "Sheriff Hood" is Deva's real father, but his ex, Carrie, has long-since married Gordon, a former marine, current lawyer, and genuinely nice guy. Gordon is killed when he helps Hood and co. rescue Carrie from an unhinged military man, but Lucas and Carrie go their separate ways afterwards, though Deva does learn who her real father is.
- Danny "Danno" Williams and his ex-wife Rachel play this trope to the hilt in the Hawaii Five-0 reimagining; however, as of the season one finale, Danno stays in Hawaii while Rachel (pregnant with their child) and their daughter go back to Jersey and she begins to divorce her second husband. Time will tell what happens to their relationship from there.
- Ray Drecker, Thomas Jane's character in Hung, essentially follows this trope.
- Innocent: To the delight of his daughter Elif, Yusuf and his ex-wife Feride grow close again after her new boyfriend Tunç is revealed as a cheating bastard.
- Shows up in Justified. Protagonist Raylan is divorced due to his temper and his ex-wife's fear that he'll die in the line of duty. Before the series begins, she's remarried to a boring, "safe" realtor. A few seasons in he's killed off by the local mob in an attempt to frame Raylan. The protagonist eventually gets back together with his ex-wife, but they're shown to be separated again in the epilogue.
- Earl Hickey of My Name Is Earl is a divorced father (his first wife left him for a mutual friend while he was doped up on morphine at the hospital). His children, however, are still young enough not to resent him for leaving, and even refer to him as "old daddy," and he finds out that Dodge actually is his biological child.
- The father in Unhappily Ever After reluctantly does this. After they divorce in the first scene of the first episode he moves into a bachelor apartment; then eventually moves into the basement of his former home; and finally back upstairs with his wife. Then his wife is killed off so they could give more screen time to The Hot Chick.
- Jimmy McNulty of The Wire is the first dad. He doesn't exactly win in the getting-back-together sense, but otherwise the trope applies.
- This is part of the storyline of Mutatsu, the Tower Social Link in Persona 3, minus the step-father.
- If you see the toys-as-parents theory, then Woody of Toy Story is like this, being Andy's favourite toy, even more than "stepdad" Buzz Lightyear.