Before Sean, for now an "only", I had two Yorkies. They were 2 years apart in age, from same parents, and got along great. I was working when they were young so they had each other for company. Also, when I went away, they were boarded together.
Since I'm home more now, Sean is fine as an "only." When we go away he stays with his foster mom and her two Yorkies...at Yorkie Camp.
