Here comes the bridesmaid! Mila Kunis and Ashton Kutcher headed to the altar this weekend -- not to tie the knot themselves but to celebrate her brother Michael Kunis' wedding to Alexandra Blacker in St. Petersburg, Fla.
After flying in with her parents earlier in the week, the Ted actress was joined by her boyfriend of nearly two years at the Cathedral Church of Saint Peter.
"Ashton was welcomed by Mila's family," an eyewitness tells Us Weekly of the Two and a Half Men actor, 35. "They seemed very comfortable together. He watched the ceremony from the front row and never took his eyes off of Mila."
The Black Swan star, 30, served as a bridesmaid for her then-future sister-in-law, donning a pale-pink strapless dress with a ruched, fitted bodice and a full skirt. She also wore a simple gold band on her left ring finger, though a source tells Us it didn't look like an engagement ring.
After the bride and groom had been pronounced husband and wife, Kutcher joined Kunis' family at the altar for pictures. Her parents "wanted to include him," the onlooker notes. "They definitely treat him like a family member."
Kutcher, for his part, really got into the spirit of the wedding. "He was holding Mila close, and they both had huge smiles on their faces," the eyewitness tells Us of the former That '70s Show costars. "Ashton had his arm around Mila at all times and was always checking in with her. They did some goofy poses, too, and they seemed to be having a lot of fun."
The fun continued at the wedding reception, held at a nearby yacht club. "Mila and Ashton had a great time dancing and hanging out on the patio," the source says. "They were some of the last guests to leave at the end of the night."
Time will tell whether "I do" is in the couple's own future, but engagement rumors have been rampant ever since Kutcher reportedly finalized his divorce from ex-wife Demi Moore in late November. Kunis has grown close with the actor's family and was even spotted grocery shopping with his mom shortly before Thanksgiving.