No expert me, that's for sure. But, I've always had 2 female dogs at any given time. One, however, was always a lab. Don't know if that makes any difference, i.e. type of breeds getting along well together. I was thinking that maybe because labs are known for their gentle temperment, it might have made a difference. My Cody and Star (husky/shep and lab) get along great. They can eat and even share bones together without fighting! Interesting that 2 females are considered the worst combo! Guess we're all a little biased thinking the males would be more aggressive!