Always hard making that decision, but look on it as your last act of kindness to a loved family member.
Very sorry to hear about that @Ponders Revisited I used to take a small dog for park walks every Sunday, for a neighbour who wasn't very mobile. Quite ill in fact. For three or four years I used to look forward to taking Buster for walkies at the weekends. Always thought that was a great name for a dog. But he was quite old, and he passed away suddenly. I was really upset at the thought of never seeing him again. Much more than I would have imagined. His owner was heartbroken. You'll do the right thing I'm sure. But I know it won't hurt any less. Best wishes.
Toughest decision ever - on one hand you don’t want to give up on them and on the other you don’t want them to suffer