Fathers' Day (1997)

Munich lawyer Thomas is a happily married father who has a mistress, Suzanne. Suzanne wants to get pregnant with Thomas. After several failed attempts, they soon learn that Thomas is sterile and always has been. Who, then, is the father of his kids? Going back through the family albums, Thomas thinks the father may have been one of two friends who vacationed with him and Bettina back in the 1980's. Thinking that the truth will out if the friends are brought back together, Thomas invites them to stay at his house for awhile.