Broken Flowers (2005)

When his latest girlfriend (Julie Delpy) leaves him, retired computer magnate Don Johnston (Bill Murray) has no greater ambition than to sit around the house. When he receives an anonymous letter from a former girlfriend claiming he has a 19-year-old son he's never met, Don doesn't even think to follow up. It's not until his neighbor, a mystery fan, encourages him that Don resolves to visit the exes who seem the most likely candidates and find out the truth.