I am fascinated that 2 Yorkies would be jealous of a new addition. That answers that question for me. I always thought Max was jealous when Teddy arrived because Max was an only child up to that point.
We narrate the doggies thoughts too.
We also say crazy things to them, and would love to know what they are thinking. For instance, after I put on their harnesses, I tell them, "You go down the hill and come right back, and don't talk to any strangers along the way." They tilt their heads as if to say, "whaaat?"