Jackson is spot on....Ive got mum n daughter (shes 18 months) and ive had to split them up on occasions once they reach a certain age theres no loyalty especially if mum goes on to have more pups

I also until a few days ago had mum and son but he tried to domineer her and they had many fights so much so i had to rehome him

Maybe it depends on the breed im just telling you my experience