My Father's Wife(2003)

Samantha is a devoted and loving wife. Unfortunately, her husband Donald is just the opposite...constantly lying and cheating, not to mention the fact that they are always fighting. Stuck in the middle is Donald's son Brian from a previous marriage, who tries hard to keep the peace in the household without much success. Miserable, Samantha soon finds herself developing an attraction towards Brian. Brian is sweet, compassionate, so unlike his father and oh yeah not too hard on the eyes either.