I am sorry to hear Maui lost that much weight. Are you sure he lost it in such a short time - then he definitely should see the vet. But on the other hand it would be good if he didn't gain it because 12 lb is better for him regarding his size.

I also am sure that your parents feeded him. If he just had been hungry he would have shown you very quickly that he needed food

The other thing: Of course he loves you. And of course they have favorite humans. Don't believe what somebody tells you. Believe in what you feel