Oldest cat -no health problems but peeing & pooping

My oldest cat is an 11 1/2 yr old male. I have 6 cats, 1 dog.
The youngest cat came on board in October and I don't think the problem is with her, they get along fine.
The problem started about one month ago, Skeets started peeing & pooping in front of the bathroom door. Now he has had attitude all his life but this has gotten out of hand. I brought in to the vet, yes he had a UTI, now clear, all kidney & blood sugar tests were negative. I have even consulted a pet psychic. He is on her daily talk to list and I have done all he has asked. Given him soft food, more attention, changed bathroom cleaning chemicals. The peeing is now daily and I am considering euthanasia which is breaking my heart.
I am on my last thread for what to do. I am shampooing the rug daily , have tried all the anti-smells- you name it ( except for vodka). I even bought pee pads - he did his business on the outside of the pads now marking a new spot..arghhhh.
His father ( different owner) did the same thing 6 months ago but was diabetic.
I just don't know what else to do. Is he trying to tell me he is too old, it doesn't seem like it. he is overweight but still agile.
HELP!!!!!!!!!!!!!!!!

have you tried just replacing all the litter pans? Throwing out the old and putting in new ones? Putting a lot of boxes in the house, more than normal to see if this helps? Perhaps the new cat ambushed him in the litter pan and now he doesn't care to use that one. It sounds like you have covered all the important bases, you might think about a cat behaviorist in place of the psychic.

It is time for a drastic move. If you really want to save your cat's life (and your rug) please do the following.

Confine your cat to the bathroom. Make sure there is a large litterbox (since he is overweight) and food and water. Make sure that you scoop at least twice daily. Keep the cat confined until there are no more accidents. (yes, I know the cat will be miserable and that the bathroom isn't big enough to do this, but if you want to save his life, it is worth doing.)

During the confinement, clean all peed on and pooped on spots with an enzymatic cleaner. Do this multiple times to ensure the smell is removed. Also, once dry, sprinkle a fruity-scented carpet powder on the spots and let sit for a couple of days before vaccuuming.

Once the cat is using the litter box 100%, start letting him out of the bathroom, but only when you can supervise his every move. Across the next week or so, start leaving him out a little more often, but make sure he is confined long enough to pee and poop in the litterbox several times daily. If he has an accident, start the 100% confinement again.

This re-training is a real bother, but it tends to be successful.

UTIs often re-occur, so it might be a good idea to have him re-checked by the vet. One of my cats needed three rounds of antibiotics before her UTI was cleared.

Hello again! I am assuming that you tried all of the suggestions in this thread?

He just received his last shot of antibiotic today so the UTI can't be a recurrence. I have 6 large litter boxes and that has never been an issue, he will go running downstairs right to the box if I catch him being naughty. Skeets is so laid back he doesn't really care if anyone bothers him, so I don't think it is any of the other cats.
Locking him in the bathroom seems so extreme and it would have to be in the bathroom in the basement, away from everyone but near the litter boxes. I don't know how he will handle it but I will try. He is so social with the family it will be very hard on him to be isolated.
If I put a new pan elsewhere in the house or near the "sight" than sure as white on rice the other 5 will be using it so that won't work.
Thank you for the advise. I'll keep you updated.

Good News- So far Skeets has been out of isolation for four days with no incidents.
I think he enjoyed being away from the other cats with his own litter box, food and privacy. There were even times he didn't want to come out of the room. Hopefully we have reached a mutual ground and no more problems. Thank you so much for the suggestion !!!!

What wonderful news!!!

Sometimes the drastic solutions are the best ones. I am so glad it helped Skeets get his behavior under control!