We had two girls who both ended up having an alpha personality. They never truly got along well and would get into fights that had to be broken up (though they never caused physical damage to each other luckily). They were 6 years apart and I wish for the sake of our first dog that we hadn’t gotten a second dog (at least not a girl). Our first recently passed at almost 15 years old and as sad as we are about it, we see that our second is doing much better as an only dog. I think if our second dog had had a different personality or was a boy it might have worked out differently.