Conversation so far:
Who were the other members of the Belmonts?
Carlo Mastrangelo, Fred Milano, and Angelo D'Aleo.
Did they know each other from school?
CANNOTANSWER.
How old were the members of the group?
No One Knows.
what was the groups most popular song?
I Wonder Why" (on their newly formed "Laurie" label) made No.
22 on the U.S.
charts.

Question: when did the group split up?
Self-contained rewrite: when did the Belmonts split up?