My Dinky is not very social. He must have visited our son's dog who is playful, gentle, and patient 20 times before he finally figured out that it could be fun to play. (for a while there, son's dog ignored Dinky...some sort of dog message was being sent).
It takes lots of patience, and it'sad to see them miss out on the fun. My guess is that since your guy has a "sibling", he will eventually figure it out.
Good luck! |