Unlike childless characters who undergo a Relationship Upgrade, single parents have their kids to think of, and their offspring will need an adjustment phase. This trope is about the blended family unit formed by the union of the two single parents, as well as the growing pains this entails.
Like any family story, there are several ways this premise can go. On the parents' side, they might clash over their different parenting styles and dynamics with the children, have trouble winning over their new stepchildren, or the exes (if still alive) might pop up and cause drama between the parents or with the kids. On the new stepchildren's side, they might dislike each other, like each other too much, worry about how the new stepparent will treat them, or disapprove of the parents' relationship, possibly to the point of Relationship Sabotage. They might even want their other biological parent back and might tell their new stepparent "You're Not My Father". And of course, adjusting to living with more people is hard no matter how nice everyone is to each other, especially if the combined family winds up with Massive Numbered Siblings.
The amount of drama the new family brings can vary — learning to get along might form the whole plot of the work, or the first thirty minutes. Usually, the blended family will settle into a more harmonious dynamic by the end...unless they veer straight into Dysfunctional Family territory.
The Wicked Stepmother generally does not feature in modern iterations of this trope — it's usually the Good Stepmother who tries to keep the peace in Dom Coms, but the former might see mileage in older works, usually with her own horrible children. Remarrying for Your Kids might feature this in the aftermath. See also Nuclear Family and Happily Adopted. May include Flirty Stepsiblings or Half-Sibling Angst.
- Citrus heavily blends (get it?) this with Flirty Stepsiblings. Yuzu's single mother remarries out of the blue, and Yuzu gets off on the wrong foot with Mei before even finding out that they're now stepsisters. Of course, their mutual attraction does throw a wrench into the whole "stepsisters" thing. Later, the manga also reveals that their parents' new marriage is a Sexless Marriage, and Yuzu's mother only married Mei's father so she could care for Mei.
- The Inciting Incident of Little House with an Orange Roof is when a single dad and a single mom are tricked into buying the same house. Along with their children, they gradually come together to be a family.
- The Adam Sandler and Drew Barrymore vehicle Blended, where they play single parents Jim and Lauren who wind up taking a "familymoon" together along with all their kids. During the trip, Jim and Lauren grow closer and bond with the others' children, who also begin to get along despite initial awkwardness. The film ends with the parents affirming their desire to be with each other (to the delight of their kids).
- The short film Jurassic World: Battle at Big Rock features a blended family with three children: one from each parent and a baby from both parents. The two older children don't get along, but when the family is attacked by dinosaurs, the children help each other.
- The film Step Brothers has a middle-aged variation, starring two manchildren who now have to learn to live with each other after their single parents get married.
- This House Has People in It: The series is about a newly-blended family, with Tom and his son Jackson moving in with his new wife Anne, her daughter Madison, and their grandmother. It's mentioned in one video that they're all having a hard time adjusting, but that Jackson is having the hardest time, especially since he's stuck sleeping in the same room as the grandmother. Madison, meanwhile, finds him weird, and she is reminded by Anne that they need to be more mindful of how they share the space in their house.
- Widowed Abby's three sons clash with widower Jake's daughter in With Six You Get Eggroll. Although the children make sure neither of the single parents are comfortable in their own houses, Abby and Jake fall in love anyway and elope — but neither of their houses are large enough for the combined family.
- Yours, Mine, and Ours: Frank and Helen have altogether eighteen children from their previous marriages, and the film is about making their marriage work with that many people involved.
- The Babysitters Club:
- Downplayed with Kirsty and her new stepfather Watson. She initially acts like a brat to him, but eventually accepts him as part of her family. She also bonds pretty easily with her new stepsiblings.
- The series mines some drama from this trope when Mary Ann's single father Richard marries his high school sweetheart, Sharon (Dawn's single mother). Although Mary Anne and Dawn are good friends, they take some time to get used to the notion of a stepfamily. They soon get over it, though, and Mary Anne also develops a good relationship with Sharon. However, Dawn later begins to miss California enough to move back there to live with her biological dad.
- Cinderella: Ella's father marries her Wicked Stepmother, who (alongside her own abhorrent daughters) treats her abominably.
- Downplayed, but present, in Daughter of the Lioness. Sarai and Dove both lost their mother very young, and after grieving, their father married her best friend, Winna. Nearly adults by the time the story begins, the two do love their step-mother and half-siblings, but are sometimes frustrated by her presence. Winna, for her part, is afraid they don't respect her as they would their real mom. When Sarai escapes the country and elopes, she assures Winna that she loves her.
- The Romanian novel Morometii is about two different families united through marriage. Ilie Moromete's three sons Paraschiv, Nila, and Achim don't quite get along with Catrina's daughters Tita and Ilinca, and their hate for their mother is even greater. Moromete's sister also hates his new family, and even manages to turn the boys against their own father.
- Subverted in the Nursery Crime books. The Genre Savvy Detectives' Guild expect and demands that detectives have dramatic, tragic home lives. As part of Jack's continued defiance of the tropes expected of him, he has a very harmonious family life. He's Happily Married to a woman with children from a previous marriage, who get along great with his own children.
- The Sisterhood of the Traveling Pants: Carmen is coping with the fact that her father, without telling her, is marrying a new woman, complete with kids, and the fear that he's replacing her.
- In the backstory of Robert Westall's The Wind Eye. When Bertrand and Madeline married, each had a child from a previous marriage (Beth and Mike). By the opening of the book the children get on quite well with each other, which is more than can be said for the adults.
- The Brady Bunch comes together when Mike (a single dad to three sons) marries Carol (a single mom to three daughters), and the show is largely about the new family's shenanigans.
- There is a minor amount of dramedy regarding this trope on Brooklyn Nine-Nine when Boyle and Gina become stepsiblings through their respective single parents, as they had been Friends with Benefits previously. Boyle's father also gets cold feet about the wedding, as he jumped into marriage after only knowing Gina's mother for a short period of time. Later, the marriage ends after Gina's mom cheated on Boyle's dad.
- The titular characters of Drake & Josh are stepbrothers with opposing personalities. The first episode is about their parents' wedding announcement, and ends with the two eventually accepting each other as brothers. Throughout the rest of the show, they're united in their dislike of Drake's little sister Megan.
- Season two of Glee had a subplot about Finn's mom Carole finding her Second Love in Kurt's dad Burt. Both boys had their issues with the relationship and feared the new family (Finn worried that Burt would replace his deceased father, Kurt worried that Burt preferred Finn), but eventually became close stepbrothers. Not bad for two guys who started out with a Gay Guy Seeks Popular Jock dynamic!
- Life with Derek is a sitcom about the newly blended Venturi-McDonald family, where the leads, new stepsiblings Derek and Casey, notably do not get along.
- A big aspect of Modern Family is about the relationship between Jay and his young step-son Manny after he marries his new wife Gloria.
- In Step by Step, parents Frank and Carol marry...but their respective children know and dislike each other right off the bat. The show is about them learning to get along.
- Stranger Things: Billy and Max are new stepsiblings through the marriage of Billy's father to Max's mother, but it's explicitly an unhealthy and unhappy dynamic. Not only are things strained from their move to a small town in Indiana, but Billy is controlling and verbally abusive to Max because his father is physically abusive, while Max's mother doesn't intervene. And that's before the Big Bad takes advantage of Billy's vulnerability.
- The Jim Henson sitcom Aliens in the Family was about a man named Brody (yes...) who has a son and a daughter, and who marries an alien woman with three kids. Culture-clash Hilarity Ensues.
- After Alicia Keys' ex husband, rapper/producer Swizz Beats, married musician Mashonda Tifrere, Keys wrote the aptly titled "Blended Family (What You Do For Love)" to reflect on the experiences of the children of both marriages and the tension between them and their parents.
- The titular characters of Kevin & Kell are a rabbit and a wolf who got married, with each being a single parent before. Kevin the rabbit was divorced and had an adopted daughter who is a hedgehog, and Kell the wolf was a widow who had a son. Shortly after the start of the comic, they have a child together who looks like a rabbit but eats like a wolf. Kell's son Rudy doesn't respect Kevin in the beginning and it takes a long time for them to bond.
- Forest Hill starts going in this direction when Colin, a fox with a son and daughter, and Flora, a rabbit with a son and a foster son who is an otter, start dating each other and helping to take care of each other's children. Thing are complicated by the fact that several of the characters have experienced sexual abuse.
- One of the central themes of The Cleveland Show is fatherhood and learning to live in a blended family — specifically one formed by Cleveland, his old flame Donna, his biological son Cleveland Jr., and his stepchildren Roberta and Rallo, with whom he doesn't quite get along.
- In the latter half of Clone High's only season, Joan learns that her adopted grandfather has been dating the adoptive mother of her mortal nemesis Cleo, and then a storm destroys her house, forcing her and her grandfather to move in with Cleo and her mother. She's not thrilled about it, to say the least.
- OK K.O.! Let's Be Heroes: After Venomous and Fink move in with Boxman's family, the episode "All in the Villainy" focuses on Boxman's robot son Darrell and Venomous's minion/daughter Fink learning to get along.
- In Over the Garden Wall, it's eventually shown that part of Wirt's frustration with five-year-old Greg is because they're only half-brothers, and Wirt resents the presence of Greg and Greg's father. Part of Wirt's arc is learning to accept and protect Greg.
- Although Princess Sofia the First has a good relationship with her stepfather King Roland and stepbrother Prince James, the same can't always be said with her new stepsister Princess Amber, who is often antagonistic towards her because she thinks Sofia will steal her thunder. Later averted, with Amber being much nicer to Sofia throughout the series due to her Character Development.
- Total Drama Presents: The Ridonculous Race: Chet and Lorenzo's single parents married one year before the start of the show and they still hate each other at the beginning of the race. They were forced by their parents to take part to in order to learn how to get along. They spend most of their episodes fighting each other, but it ends up working in the end after they discover they have more things in common than they thought.