I have a colony that is absolutely going like gangbusters. They have already filled 2 supers (but not capped) and I put a 3rd on yesterday. It is packed with bees. I noticed one queen cell on each of two frames. Assuming that the bees wanted to swarm and they needed more brood space, I took both frames with queen cells (capped brood, larvae, and bees) and another frame of brood/bees and a pollen frame, then put them in a new hive. The new hive has a medium super with 3 frames of honey and the remainder in comb.
Is there any problem with letting the queens hatch, duke it out, mate and start a new colony? Later, I would then like to join this colony with another weaker one so that it gets a new young queen. I think I've read about this type of splitting but not sure I'm doing it by the letter of the law.