Ashton Kutcher and Demi Moore's May-December romance initially sent shock waves through Hollywood in 2005. And the duo managed to shock again when they later married.
There may be a 15-year age gap between the pair, but Kutcher quickly found his place in the Moore-Willis family. Not only has he become close with Moore's three teenage daughters, Rumer, Scout and Tallulah, who affectionately call him M.O.D. (for "My Other Dad"), he also has become friends with Moore's ex-husband, Bruce Willis. The brood can often be seen palling around at events from the Super Bowl to Hollywood premieres. Kutcher and Moore even take vacations with Willis.
In a strange blending of the past and present, befriending the ex and his or her new love appears to be a growing trend among celebrities who swap partners more often than movie roles.
Kimora Lee Simmons is dating Oscar nominee Djimon Hounsou, and Russell Simmons, her ex, is supportive of the relationship.
Tom Cruise's ex, Spanish actress Penelope Cruz, attended his Italian wedding with Katie Holmes and was one of the first people to see baby Suri.
"As more people split in Hollywood, you will see more cases of this happening. It's a small community and it works best when exes get along, especially when children are involved," Dina Sansing, West Coast deputy editor of Us Weekly magazine, told ABC News' "Good Morning America."
So what's the secret to amiability between new couples and their former lovers?
When ABC News' "Good Morning America" asked Willis how he gets along so well with Kutcher, he said: "I try not to judge. It could be a lot worse, you know? He's smart and he gets the Good Housekeeping seal of approval. You have no choice who you fall in love with, and I think they make a great couple."
Sansing said the threesome makes for a good example.
"Demi, Ashton and Bruce are one of the great examples of an extended family in Hollywood. They all get along very well. It stems from Demi and Bruce having a good relationship after their split. Ashton has been welcomed into the family. He has struck a good balance of being a father figure to the children, without overshadowing Bruce. It's a great dynamic," she said.
Moore told ABC News' "Good Morning America" that one of the reasons her divorce is better than some people's marriages is that she put her kids' needs first.
"My intention came truly out of my desire to place my children as the priority, and what you have as a couple -- those were your issues, not your children's. I think, perhaps, having been the product of divorce, where I felt a little bit like the pawn," she said.
Will Smith and Jada Pinkett Smith have also made their children top priority. Smith's ex-wife, Sheree, was the first to see his then-newborn baby with Jada. Sheree and her son with Smith, Trey, were visiting a sick grandmother at Cedars-Sinai when Jada gave birth in 2000. The two women are said to be good friends, keeping it all in the family. Will and Jada even worked on a sitcom about an ex-wife, a man and a new wife trying to get along for the sake of a wonderful little boy.