This is an excellent thread to read, very interesting.
I have a 5 year old 4 pound male, he was such a great yorkie baby, then just before he was one, the vet killed my almost 5 year old, I was so sad for my baby, I got another play mate for him, a 6 month old girl. well she was out to kill, and after that he has never been the same, he was afraid of new born yorkies, after three litters he is so much better. Slowly over time, I would always put him up away from baby's, where he could watch and yet feel safe. Each litter he got a bit better. I just got a new girl this summer, he jumped right into bed with her, stund us all..
He is still aggressive when some one comes near the door, he acts like a huge attack dog.
Needless to say the 6 month old girl I got, went to my daughter, my loss on the money, but she got a good home, and now a few years later she is a much better dog, it took me three years for me to allow my dogs around her though.
pooh's mum