I also have 2 border collies, but both of mine were rescues - and both ~ 1 year old when I got them.
We had the male dog for about 5 years before we got the female. It went over pretty terrible at first with constant .... constant... constant fighting. After about a month, the female dog started following the male around everywhere and now they are even crated together.
I'm pretty amazed you were able to bring in the second dog that easy.







