I need little help about cockatiel breeding

So i have three cockatiel chicks two of which are girls ( i am not breeding them in the near future i am just asking for when they are in the appropriate age to breed and how to pick a mate for them ) so i had only one girl in the beginning then i bought the other two ( the first one was a normal and the two was siblings a girl lutino and a boy pearl ) so my mother said that the normal grey one will be with the pearl and the lutino girl we are going to get a mate for her when needed but here my brain stopped for a moment and said wait what if the normal girl doesn’t like the pearl ( they fight a lot like a whole lot ) and I don’t want siblings to mate with each other so should just leave them and not breed them then get like a couple of two cockatiels in love that will breed eventually because i don’t want to get a mate for everyone of them that’ll be a big thing to do so please tell me what to do
Sarkari job