In my 1.17 survival world, I captured a beehive that had two bees in it. I put it in a container and a few days later a third bee appeared. I thought maybe I had missed one so I didn't think twice about it, but I came back several days later and now there are about 20 bees. I did not do anything, I did not breed them, I have not even been near it, although it has been loaded. I am not running any mods it is purely vanilla and it is a single player world not open to LAN so nobody could have come in and bred them. I have no idea what happened or how they got there.