Welcome to WP and please accept my condolences on the cat...oh, and the grandparent, too.
We had an indoor/outdoor cat when I grew up and he was my best friend. I think I was his favorite human. And I only met one of my grandparents. She died when I was 19. My parents sent me the news of her death by mail. When the cat died, a few years later, they telephoned me to give me the bad news.
When I married my bride she had two elderly cats. One was outgoing and friendly, the other was a scaredy-cat who hid from strangers. She even hid from my future-bride for some months after moving in with her. The first time she immediately showed interest in one of my future-bride's friends it was a guy who did not like cats—I figure giving him attention was some kind of kitty-cat sense of perverse humor. The second (and only other) time the kitty immediately liked someone was me! I think that endorsement carried considerable weight with my future-bride. The cat and I became a couple. Whenever possible she would hang out with me and she seemed to begrudge my bride being around me. She couldn't keep her paws off of me. This kind of hurt my bride's feelings, by the way. She felt like the cat had dropped her; but I would try to reassure her by pointing out that the cat had retained her on staff.
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When diagnosed I bought champagne!
I finally knew why people were strange.