Moore made his last appearance onY&Ras Neils brother in September 2014.
Rowell, who played Neils wife, was a fan favorite from 1990-2007.
Morgan played Hilary Curtis, Neils former cheating wife, from 2013-18.
Monty Brinton/CBS/Getty Images
TheY&Rplot line will address St. Johns passing beginning April 23.
The story will continue through the remainder of the week.
St. Johns last appearanceonThe Young and the Restlesswas Feb. 6.
CBS
The episode ended with the tribute, In Loving Memory Of Our Dear Friend.
He won two Emmys for playing the makeup executive.
