Ex Mousketeer Marque Lynche Jr. Dies at 34

One of Britney Spears and Ryan Gosling's former 'All New Mickey Mouse Club' co-stars was found dead in his NYC apartment ... TMZ has learned.

According to law enforcement sources Marque "Tate" Lynche's roommate found him on Sunday afternoon. He was only 34 years old. The medical examiner's office conducted an exam of the body on Monday, but hasn't determined a cause of death yet.

Lynche was a Mousketeer from 1993 to 1995 -- and shared the camera with Britney, Ryan, Justin Timberlake and Christina Aguilera. He later appeared on Season 3 of "American Idol" and made it to the semi-finals.