I've heard of it before but never seen it. I've got a 5 frame OB hive in my office that has a queen I marked. The bulk of the paint had been removed but a small amount remained. I thought I'd seen her a few times since but unmarked and thought they had completely removed the paint. I'd never seen them completely remove the paint before but there's always a first.
Today I see the queen with her little mark,... about 10 cells away is another unmarked but much larger queen. Dumbfounded I watch the large one walk up the to marked one. They sniffed each other and moved about their merry way with workers giving them both interest and a wide queen birth. They are both clearly queens, but I would believe it if I didn't see it myself. It'll be interesting to see if they'll both over winter and I'll separate them if they do.
Does anyone have experience with 2 queen hives overwintering?