My cat, who I call Big Cat, his real name is Francois. He used to weigh 23lbs, not fat just big. Any way I've had him for 15 years. He's the best cat and he never swipes or hisses at the Bs. This cat is a real trooper!
Awww - Looks like your B and Francois live in sweet harmony. Big Cat is really cute, love his soft grayish color. What is your B's name? I can't remember if you had made mention. I remember Ringo.
IM so sorry for your loss … it almost sounds like feline leukemia or feline aids... we had 2 litter mates die from it... And the symtoms you describe sound all to familar ... You might contact your vet and ask questions... If you have other cats, this is a highly contagious desease.