My true condolences. We lost two fur kids recently.
My wife went to San Diego in December to help her mom after surgery. While she was gone, one of our cats started meowing frantically and dragging himself across the floor, hind legs paralyzed (my wife used to tell me she had that cat longer than she had me). Took him to the vet, nothing to be done so I held him and let him go quietly. I was never a cat person but had become one. The cat and I used to watch action movies together.
Then, March 30th, our border collie rescue Belle (the dog in my avatar, sweetest dog I'd ever known.) screamed in the night and went into seizures--4 in 7 hours. First thing in the morning, vet said she'd had a stoke, and would die in seizure. We never knew how old she was, but held her between us while the vet helped her go peacefully. Both were horrible experiences and our hearts were/are still broken for both of them.
They were better people than most people I've met.