This could make for an uncomfortable family reunion. An adviser working for the hedge-fund manager who sued the New York Islanders for reneging on a deal to sell him the team is NHL Commissioner Gary Bettman’s half-brother, The Post has learned. Andrew Barroway hired Jeffrey Pollack several months ago after reaching a handshake deal to buy the club from owner Charles Wang for $420 million, sources said. Wang and Bettman are believed to be pals. Barroway also hired David Carlock, a sports-marketing specialist, as a late addition to help in his Islanders bid — which ran into trouble, sources said, when the Philadelphia lawyer and hedge-fund executive had trouble raising the money needed for the purchase. Barroway says he had the funds. Wang in mid-July unexpectedly raised his asking price for the team from $420 million to $548 million, making it nearly impossible for Barroway to complete the purchase, the lawsuit claims.