I got a swarm about 3 to 4 weeks ago in my backyard. It had 3? queens in it. I didn't know it was multiqueened until I looked a day after boxing it. The bees were balled tightly into 3 balls in different places in the box. I figured it was multi queened, so i poked thru one of the balls and sure enough they were keeping a qeen in there. I tried to cage her but she kept going back into the ball. Then when I kept after her, she flew off. The other 2 balls I just left alone. A week later, I had one laying queen in the box. I've heard and now witnessed that there are swarms with multiple queens in the fall of the year.
20+ years, raise my own queens, feed when needed. I treat, but have not perfected varroa management yet.