[PlayingPretend]

This sounds like Maury for dogs.

Honestly, the only thing I can think to do is get a DNA test done or ordered of both dogs and the puppies. Then again, all that does is prove your dog sired the pups. Nothing really you can do without having signed a contract in the beginning about the terms of who has "custody" over the pups.

Personally, I disagree with backyard breeding, as I take it there aren't any homes lined up? If I were you, I'd make sure the pom's owner knows you're willing to take on the pups he can't find homes for and find homes for them yourselves. It'd be a shame to see them end up in the shelter. I wouldn't put it past him if he's denying that your dog is the sire. =/