I made a verbal agreement with my daughters boyfriend when they were living together .I bred my Rottweiler dog and gave him a puppy with the agreement that if anything ever happened that he could no longer care for the dog or something happened to him the dog was to be returned to me . He just recently passed away and his family is trying to give the dog to some one else. I no nothing about this man or how the dog will be treated or if he will keep it in the house or outside . The dog was raised in side the home. Do I have a rihgt to sue to get this dog back . The same agreement was made with several of my other puppies I gave to people

You have no proof so Its up to a Judge to listen to both sides and determine.

* having a witness can have some bearing

The issue here, the verbal agreement was made with a man who has died. So the verbal agreement died with him. Also I doubt such agreement is enforceable, since after ownership is transferred, he would have right to do with dog as he wishes.

My opinion, you have no legal standing in this, there is no proof of agreement, and even if it was, I do not see it binding on the heirs, This is property and will pass to heir of estate.
If they do probate, you can try and make a claim for animal.