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Other than the name Dion, no. The Dion from Dion and the Belmonts is Dion DiMucci (Dion is used as a first name, not a last name).
Dion DiMucci is not Céline Dion's brother.
No, Celine Dion is not single.
Céline Dion has five brothers:
Celine Dion is a pop singer.