This movie is about a husband and wife who have a baby. They unfortunately die in a motorcycle accident and the baby is left to the womans best friend and mans best friend who hate each other. At first they hate each other and then they fall in love and learn to take care of the baby.
You are thinking of the movie "Life as We Know It", from 2010. In it, there is a couple that falls in love, marries and has a baby. They die in an automobile accident, and while the respective god parents don't like each other, they come together for the sake of the baby and end up falling for each other.