This began when we had to be gone a lot for hospital stays. If we were gone overnight, he would pee on her side of the bed. Our final hospital stay lasted just over a month, and our cat (Boots) stayed with a friend where he didn't have any problems going outside his litter box, even with a new litter, so I don't think it is a litter or health issue.
Now that my wife has passed, and the cat is back, I have been using the litter that our friend was using, but the cat pees on our bed at least once per day. A couple of times while I was in it.
Boots often sits on my lap in the evenings for a couple of hours (in between getting up to take care of the kids), so I am giving him as much attention as I am able.
Although I am not particularly a cat person, I don't want to get rid of the cat because the kids just lost their mother, and don't need to loose their cat too. But if this doesn't stop, he's going back to live with our friends who were taking care of him before.