Firstborn (1984)

A teen must protect his family when his mother's sinister new boyfriend begins exerting his authority in their home.

About

A young teenaged boy named Jake has been the man of the house ever since his parents divorced a few years before. While living with his mother, she began dating a man named Sam, who struggles with drugs and alcohol abuse. Unsure of his mother's boyfriend's source of income, young Jake begins to dig around for answers. 

Trivia

Actor Corey Haim was nominated for Exceptional Performance by a Young Actor- (Motion Picture) during the Young Artist Awards back in 1986. Prior to Peter Weller being casted for the role of Sam, actor Tom Berenger was also being considered.