This is so hilarious! The breeder from whom we got our 2 yorkies breeds Great Danes AND yorkies, and those are the only 2 breeds that she breeds. I thought it was SO funny that she bred the largest breed in the world and the smallest breed in the world! Looks like there are more of you out there! Do you have a picture of them together? I would love to see them!
Sorry I don't have any advice on the humping issue. All I can think of is the dominance issue.
