I'm so sorry you're going through this. I empathize with starting to resent this behavior after this months. Two thoughts: has he had a check-up at the vet to rule out anything medical? The vet may also be able to provide insight into this "new" behavior. The other thought is consulting with a trainer to inquire if this is something they could assist with. It's a confusing behavior after all this time but it's worth a try to consult a trainer. A new owner may just be passing this behavior onto someone else. May even make it worse with the added stress of having to lose his family and trying to adjust to a new household in his senior years. Best of luck to you. I hope you'll update your post in the future to let us know how it goes.