Conversation so far:
Who were the other members of the Belmonts?
The other members of the Belmonts were Carlo Mastrangelo, Fred Milano, and Angelo D'Aleo
Did the members of the Belmonts know each other from school?
The other members of the Belmonts were from the same neighborhood as Dion DiMucci
How old were the members of the group the Belmonts?
They were adolescents
What was the Belmont's most popular song?
The group's biggest hit, Where or When, reached No. 3 on the U.S. charts

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