Are you thinking of trying to find out if you can get him neutered through some assistance program? That might help. Are there any rescue groups in your area? They usually foster in someone's home, and your cousin would have to go through some sort of process/evaluation to get him back, though at this point, I wonder if she really wants him. ::sigh:: Anyway, I really think the cat deserves better than her, and since he's not getting along with you....
That darn cat