>>Yes, that's kind of what we have been trying to do. We tell him "no." (Seems he's trying to assert his daomnance. We want to remind him of our dominance over him.)Try to get him to do something else, and praise him when he plays nice. However, he's so obsessed that there just is no distracting him. It's constant.
>>
>>He's such a jerk. It's a good thing I love him.
>>>>>>>>>>
Telling him "No" and trying to assert your dominance won't help. Distract him. If necessary, put a leash on him and the other end in your hand. Get him into other activities. If he's not neutered, that truly needs to be done. And you don't actually want to stop every single second of this humping. Normal dogs would be doing this during the initial period of getting to know one another. It's play, not just dominance and not just sex. They have to learn each other's moves. My female 7-month-old pup humped my 7-year-old male dog like crazy the first few days, and then never again. He never objected to it. He was very dog-savvy and so was she. Until his hips got arthritic, he would hump one of "his" two females from time to time, and I'd simply call him to me when I noticed.
Your dog has an established habit of doing this with the cats that should have been interrupted long ago. That means you may have to work a lot harder at it now. And again, if he's not neutered, do that. An enlarged prostate becomes inevitable in an intact male dog with age, and these often get infected. That, too, would be causing him to hump. He needs other things to do. You could teach him, and he may learn with the new dog, too.
No pup should be left alone with an adult dog until at least 4 months of age, often older. That will also help control this situation. At some point, she will tell him "no." Let her. Back her up. He will likely accept that from her. But this is not about your dominance and not really about his, either.
In a male/female dog relationship, there is not a clear dominance needed. He is top male and she is top female. Typically, he plays a "protecter" role, and she has the right to say "No," to protect her pups, to decline mating. Never feed two dogs together or leave any highly desirable chews or toys out for them to compete over.
Train each of them individually away from each other so they don't become bonded only to each other and not to humans (especially the pup at this point).
If this is an obsessive behavior on his part, you can get some ideas on how to handle that, as well as humping and other things, at the link below my signature. It's a free, veterinary-sponsored site that does not require you to register, since only edited material is ever posted.
-----
Kathy Diamond Davis, author, "Therapy Dogs: Training Your Dog to Reach Others," 2nd edition, and the free Canine Behavior Series articles at http://www.veterinarypartner.com/Content.plx?P=SRC&S=1&SourceID=47
