Try clicker training. It works wonderfully for many people, and it eliminates the possibility that dogs respond only to a certain voice if they are trained only with voice commands. Also emphasize hand signals.
Make sure each member of your family works with Kopper.
While many Yorkies bond strongly with one person, many also bond with more than 1. My boys love their grandpa as much as they do me, and Max has bonded with my brother as well.
__________________ Kristin, Max and Teddy
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