Sounds like their having a Power struggle? Who is usually "Alpha" in your Pack?
You need to step-in the moment it starts, regardless of who starts it?
Correct them now before it gets out of hand, that way you seem like the "Alpha" always in control. I have 2, but 1 is a male and the other is a female so it's easier IMO, to keep them in check, b/c even though they are adorable they do have that "Small mans complex", even the females do.
Hormones kick in too? It's hard to say what causes it w/o knowing more details? Good Luck, Aloha*
