4 Seasons fans: What two keyboardists (in different editions of the group) had hits with their prior bands?

Answer 1

Bob Gaudio performed with the Royal Teens, and had the hit "Short Shorts"

Jerry Corbetta was a member of Sugarloaf, who's big hit was "Green Eyed Lady"

(and you're right about the Dion question...lookin forward to the answer on that one!)