Jason and Julie live on different floors of a Manhattan apartment building with a doorman. They have been best friends for many years but are not attracted to each other. They have both had difficulty finding a romantic partner, and at 4 in the morning when Julie calls Jason asking which way to die he would prefer, both of them are in bed with someone. He is in advertising and she describes her job as finding ways for a rich man to use his money to benefit others.Jason and Julie get together with four friends at a nice restaurant. Jason is not with the woman he was in bed with, and they are likely to break up. Leslie and Alex are already at the table but Ben and Missy are in the restroom and when they come back, they look quite happy, as if they have been doing something naughty. Nearby are misbehaving kids, and the friends wonder why anyone would bring kids to a nice restaurant. But Leslie and Alex have an announcement: she is pregnant.Once Leslie and Alex have their baby Cole, Jason and Julie visit, and Leslie is angry because she feels Alex isn't doing enough. Julie wants kids and time is running out. She and Jason, on their way home from a birthday party for Jason, talk about different types of relationships and ways she could have a child. It appears relationships and children don't go together.Four years have passed since the start of the movie. Julie and Jason decide they can have a baby together but not be a couple, because being a couple interferes with the joy a child would bring, and children hurt relationships. They announce their plan to Leslie and Alex, who feel insulted about the other couple's attitude toward relationships and children but are somewhat accepting. Then Julie and Jason make their announcement to Ben and Missy. In another room, Ben and Missy say their friends are doing something crazy. Eventually, Julie and Jason decide to go the traditional route to get pregnant. Jason needs help getting in the mood so they watch porn.Jason is on a date with a woman who pronounces French wines perfectly when he gets a call. Julie is in labor. Jason goes to the hospital and helps out. Once the baby is born, there are visits from Julie's widowed mother Elaine (she's not a widow, she says, because he left them and remarried) and Jason's parents. Elaine wants to be involved and babysits several times, while Jason's parents leave quickly after giving Jason a check to help with expenses.Jason and Julie are shown taking care of baby Joe both together and separately. Julie goes for a run in the park when she gets a break, and there is snow on the ground. Sometimes things go well, and sometimes they don't. Julie gets naked in front of Jason and asks if she's ready to date and Jason says it will be a few more weeks.The four friends come over to visit, believing Jason and Julie will be frustrated and tired. Alex and Leslie have a second child with them, and Ben and Missy have a child as well. In fact, Jason and Julie are coping very well, at least at this time.While taking Joe to the park in a stroller, Jason sees the beautiful Mary Jane struggling with a large dog. It's not hers, but a neighbor's. Jason introduces himself and tries to explain his situation in a way that won't keep Mary Jane from wanting to go out with him. After some effort, he is successful and they end up in a relationship that goes better than others he has had. Mary Jane is a dancer in the musical "Chicago" and very flexible, which makes their sex life amazing. She doesn't want kids but is willing to deal with Jason having Joe.Julie is less successful in her dating life, going on several dates with men she doesn't want to date again. Jason's success makes her cry and she turns to Leslie for comfort. Things are going better for Leslie and Alex, by the way. Eventually, Julie attends an elementary school event with Leslie and meets the very handsome Kurt, who is divorced with kids. They hit it off. Kurt doesn't want to introduce Julie to his kids until he is absolutely sure, while Jason's parents meet Mary Jane.After Joe has turned one, the families, including Mary Jane and Kurt, travel to a ski resort in Vermont for the Christmas holiday. They all share a cabin. While they are eating, Missy looks depressed and drinks. Things start out pleasant but there is a big argument over the nature of Jason and Julie's relationship. Ben starts ranting, saying some very insulting things. Jason defends his relationship, saying he knows Julie better than anyone and he cares a lot about her. Missy cries, and it is clear Ben and Missy are headed for a breakup.Julie tries to play the game of what would be a better way to die with Kurt, but he seems confused. He grudgingly goes along but this is the start of Julie realizing he might not be right for her.Back in the city, Jason has a similar moment with Mary Jane in a nice restaurant, where Mary Jane objects to the idea that a couple brought their kids. Jason has a conversation with the family and Mary Jane looks bored.Ben moves out, and when the friends get together again, Missy has a new man.Kurt is ready for Julie to meet his kids. Julie and Jason meet at a nice restaurant, but no one else is there. Jason admits he has feelings for Julie and would like to be with her, but Julie still believes he doesn't like her in that way, and she leaves the restaurant. Then she moves to Brooklyn. Jason hates being away from Joe but Julie says he can see Joe anytime. The previous Christmas, they sent out one Christmas card, but now they each send their own card.After Jason and Mary Jane break up, he sees Ben in a bar and forgives Ben for his rant the previous year. After they talk, Jason is convinced he and Julie can be a couple, and he comes to visit Julie with a Christmas present. Julie wants to open it later, but two-year-old Joe is insistent. The present is a photo album with lots of photos of both Julie and Jason, along with Joe. Joe wants "Daddy" to sleep there but doesn't understand why he can't. Julie makes him leave but he comes back and insists he has real feelings for Julie, and they kiss and end up in bed.