We got Dixie, our first yorkie, when she was 7 months old. She weighed around 5 lbs. A few months latter we got a second yorkie, Sissy, from the same breeder. She was around 18 months old and she weighed around 9 lbs. Sissy and Dixie got along great except for the size difference. Sissy was like a bull in a china closet and at times she would just run right over Dixie but they were good friends. Later we added a couple more females that were already adults and that is when we started having some fighting issues. Yorkies have all different kinds of personalities; some get along great and some will try to be dominating and want to fight. I think having intact females is what causes most of the fighting problems and then there is the jealousy. I do think that aggression and dominance tendencies can be inherited so it is always a good idea to ask the person you are getting your pup from about the personality of the parents. I think a alpha female will often have pups that are the same way. | 