This film is the first one based on a Neil Simon play and the screenplay is by Norman Lear. According the IMDb, Frank Sinatra's character is actually based on Simon's older brother--a playboy who apparently was quite the lady's man. While Sinatra is good in the film, he was badly miscast as he is easily old enough to be his brother's father! In fact, he and the father (Lee J. Cobb) are about the same age--and so I had a seriously hard time believing Sinatra was Tony Bill's brother.
The film begins with a young man showing up at his brother's bachelor pad. Apparently he's moving in and it's quite the surprise. However, he IS welcomed by his brother--but not the over-protective parents who want this young man to return home. The younger brother (Tony Bill) seems quite naive and he's in for a shock when he sees that his brother is quite the player--and is currently stringing three ladies along at the same time! But, when he can't possibly make all his commitments to the ladies at the same time, the naive brother is convinced to help! What's to happen to the sweet younger brother and will his older brother ever grow up and become responsible and settle down? The acting was fine in the film and the writing very good. In fact, apart from Sinatra's age, I have no serious complaints about the film. It is a bit of a trifle of a film but enjoyable throughout--and is well worth your time.