Billy Corgan Says His Stepmom Thinks Bill Burr Might Be His Brother

Shocking revelation from Billy Corgan ... he thinks he might be related to Bill Burr ... if a family member's suspicions turn out to be true.

The Smashing Pumpkins frontman was a guest on the "Howie Mandel Does Stuff Podcast" when he revealed his possible blood connection to the famous comedian.

Billy says his father was a traveling musician back in the day ... and his stepmother once told him she believed Bill was one of his father's illegitimate children that he sired while out on the road.

BC says his stepmom brought it up about 10 years ago at a party for one of his brothers ... and he says Bill looks a lot like his dad.

It's a pretty wild claim from Billy, with not much evidence to back it up.

We reached out to Bill's camp ... so far, no word back.