That’s so sad. When cats get old, everything sure changes. He’s 21? That’s amazing. You must be good “parents”.
I’ll admit that we got lucky with our strays because they pretty much coexist in peace in spite of their pathetic histories. Sometimes we watch “My Cat From Hell” and can’t believe what some people endure.
I’m not sure why this cat has been so resilient...but now we’re paranoid about changing anything. For example, we thought about giving him geriatric food, but worried changing his food might kill him, etc. And now I’m not sure he could find his way back to the house, so he only goes out with supervision.