You definitely do NOT want to allow Emily and Duke to breed! You should never allow related birds to breed. If you truly want Emily and Storm to be a breeding pair, you need to understand that this means you have to give them up as pets. They both need to be at least 2 years old. If they are old enough, you will need to cage them in a breeding cage together and stop handling them to see if they will bond as mates. Because the brother likes his sister, you need to have his cage in a different room and cut off all contact between him and the other two birds. There is still no guarantee that Emily and Storm will bond with each other, and even if they do, it doesn’t mean they will successfully breed. If these three birds are pets that you handle and interact with, I would advise you not to plan on breeding them. Pet birds do not always make good breeders and as I said, you lose them as pets if they do bond. Breeding birds should not be handled, they need to be kept in a quiet, private area with no human contact other than when you need to feed them and clean the cage.
As to the behavior, birds do not understand no, or being punished. When Duke chews on something he shouldn’t, then you need to offer him a toy or something he can have, to distract him from what he can’t have. He isn’t going to listen to you, you need to show him a toy, or simply pick him up and make him stop, and then move him to where he can play with a toy. Here is some more info on training pet birds.
Teaching Your Bird
Thank you for asking Lafeber,