I am worried about the Senior Cat

and there is nothing I can do to help.
In the past few weeks, ever since we had the break-in, he has seemed increasingly frail. He is less steady on his feet and he seems more depressed.
Today he has to go to the dentist. This is a major undertaking involving an "access cab" and a wheelchair. Middle Cat is handling that and I am genuinely grateful she does handle most of his medical issues. It is one less thing I have to do. It isn't that I mind doing things for him. I don't. I'd do anything he asked - simply because I know he will never ask the unreasonable of me.
What bothers me is that he is not really happy any more. He tries to hide it but I know he hates being so dependent on other people - dependent on them for the things he once found easy. He wants to do things and he can't. He is worried about falling (and I worry about him falling) but he still tries to do things he shouldn't do . He hates asking me to do something, indeed anything. 
A friend came to lunch recently. She had not seen him for almost six weeks and she agreed that he had deteriorated in that time.
Yesterday, wanting some paper to write something down, he found an old notebook. I saw him staring at it.
    "Is this your mother's writing?" he asked.
I told him no - and it wasn't. It was the writing of someone of her generation but I pointed out the "Ms" and "Vs" were not the same. The notes in it might well have referred to my mother and her last illness. He was quiet though and clearly upset. As he was finishing his light evening meal he said to me,
   "I often feel guilty that I wasn't there when she went."
He meant my mother of course. I pointed out as gently as I could that he had been there until the hospital sent him home and told him to get some sleep. Middle Cat and I had taken turns to be with her. Her brother had been there most of the afternoon. My godmother, a former nurse, had been in and actually relieved the staff at one point. The hospital staff had been marvellous. And, although I didn't say it, I knew my mother would not have wanted him to be there. Still, he feels guilty even after almost nineteen years. Yes, I understand that - and I can't do a damn thing about it.
Right now he is looking forward to late November. My brother will be bringing the family over from afar. We have arranged for the Black Cat to be here for two nights as well. She hasn't seen him for six  years. He needs to see her. 
It will be good for him even if I can't turn the clock back.