I was watching Larry King Live last night, and they had the entire original cast of Roseanne on (everyone but Laurie Metcalf). One of the callers asked where everyone else is, and they said that Glenn Quinn (Becky's husband Mark) had died! Not even recently, but in 2002!
A quick internet search gave me
http://www.stuck-in-the-middle.com/quinn/ which reported that he had a heroin addiction which ultimately killed him.
Sad.