Wha movie about man s son friend and son wan to know why dad didnt do to him it is an old comedy?

The son is interested in knowing about . At end of movie son, who is very youg, finally masurbates on balcony during a family diner and experience ual pleasure for the first time. The mans sister is on verge of breakdown and recieves prank calls from a man who says very suggestive things to her. It is older movie but it is a comedy.I want to know the name of the movie