Dixie, good for you, I'm glad you got this information. It sounds to me like they have given Cooper to the brother-in-law, no doubt about it.
I think they were to busy with their corporate lives to bother with Cooper and thought he could take care of himself, or left him to the kids to take care of. I think they felt they were living the perfect life with the house, the kids and the perfect dog only it didn't turn out that way. I do believe the answer is to get Cooper back and see what the problem is and the longer it goes on the worse for Cooper it will get. For goodness sake who knows what they are feeding him for one thing, how did he gain all that weight so quickly. Well, I for one will breathe a sigh of relief when you get him back.
Dixie you are the best.
Jackie