You have to keep them separated at least until the babies are 8 weeks old. That way you don't risk injuries to them by the adult ducks. There will be pecking, but that should stop fast. I had mine separated by a fence so they did get used to each other. There was still chasing and pecking when I put them together. It got less in time, and they went along just fine. The occasional pecking stopped completely when I got rid of the extra boys and only kept one boy. Pekins are large, but they are very sweet ducks. Rescue is one thing, but you also encourage those bad breeders when you buy from them. It's a do or don't, either way is has its up and down side.