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Four of the five members of * NSYNC are in serious talks about giving fans the reunion they’ve been waiting for -- even if Justin Timberlake doesn't sign on ... TMZ has learned.

Sources familiar with the situation tell TMZ ... Lance Bass , Joey Fatone , JC Chasez , and Chris Kirkpatrick have been discussing big plans for the group's 30th anniversary, including the possibility of an arena tour without JT. We're told the guys know demand is still sky high, and promoters believe fans will pack arenas even with just 4 of them. Getty

As we first reported, the foursome were eager to sign onto a massive stadium tour deal from Live Nation and AEG last August for a 2026 run. The offer was presented to all five, but Justin never engaged -- long before his Lyme disea

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