Ben Affeclk & wife Jennifer Garner

The 'Butter' actress, who has three children, Violet, seven, Seraphina, four, and Samuel, 17 months, with her 'Argo' director husband, hosted a party at their home in Brentwood, Los Angeles, last Sunday, three days after his 41st birthday, with guests including Matt Damon.

A source told Us Weekly magazine: "There were about 30 people who showed up around 2 p.m. for an afternoon party. There were kids running around in the yard having a blast. It was a relaxed afternoon and people didn't bring gifts. They all started to leave after dinner around 6 or 7 p.m."

Jennifer has formed a close bond with Matt's wife Luciana, with whom he is raising four daughters Isabella, 6, Gia, 4, Stella, 2, and Alexia, 14, since the couple moved from New York to Los Angeles over the summer.

A source said: "Jen likes to throw parties at the house, she has a clique in LA that Luc is getting introduced to."

'Elysium' star Matt recently opened up about his 'bromance' with Ben, claiming he is one of the most important people in his life.

The 42-year-old actor, who co-wrote and starred in the Oscar winning 'Good Will Hunting' with Ben, said: "We're neighbours in Los Angeles, our wives see each other a lot and we're constantly working together, surrounded by our close friends and collaborators who help us with all of our projects. His opinion is very valuable to me."