Potty training??? Cat diapers???? Help!

How long ago is a few months ago? And have you discussed this with a vet? You must rule out a health problem otherwise the resulting behavioral problem will never be resolved. Even if the vet can't find anything, try a urinary food if he can eat it.

I wouldn't try diapers in a cat that still has normal bowel and bladder control. You might make Hobbs decided to hold it and then you would have urinary tract problems or worse to deal with.

Some on here have potty trained their cats. It doesn't seem that easy and certainly not when a cat isn't even using a litter box.

One thing you MUST do. 7 cats need more than 3 litter boxes. I have 7 cats, too. I know how much poop and pee that is a day. You need at least 6 or 7 boxes, more if you can fit them.
I know it's a pain in the butt, but 7 cats means a lot of compromise. We have a box in our bedroom and one in the hallway - it means that sometimes we smell a kitty pooping while we're in bed and have to step on litter in the hallway. We live, though.

You may have to contain Hobbs to one room for a while to retrain him to using a litter box. What sort of things is he peeing on in the house? How are you cleaning them? Any carpet soiled?

Get him back to the vet pronto. Have them do a urine draw on him. He is stressed because of the all the recent additions. Stress quickly leads to bad health issues. The kidney's and stress are often closely related. A needle draw of urine is the most accurate way to diagnose the problem. Rule that out first before you go looking elsewhere.

Back to the vet, back to the vet, back to the vet... they say the third time is the charm, so that's why I repeated . The senior panel will not show you an Urinary Tract Infection, and three months ago is a looooooong time for that to happen. An UTI can happen any day, out of the blue, and it can be dangerous - especially in male cats, as if he has crystal on the top of it, he can get blocked, and die. Yep, sorry for the drama, but it can get that serious...
Cats don't just start peeing outside of the box like that - the main reason is usually a medical one, then not liking the litterbox or the litter itself (and that is the number of box, cleanliness, scent, texture, location, etc.), then stress...

You must have one box for each cat... Also, what type of box are you using? Where are they located? If they are covered, take the tops off. Many cats don't like scented litter - use unscented litter. Cat Attract Litter will do a great job in attracting him back to the litter box - there is an great guide inside of it with a lot of good information as well. HIGHLY recommend it.
If the boxes are inside of closets, remove it. Laundry room, or rooms with water heaters or anything noisy is bad too, as it can startle the cat...
Good places are on back or rooms or hallways where they can see the room, and they don't feel trapped.
Make sure to use a good enzyme cleaner to clean the spots he pees on - bleach is no good - there are cats that actually like the scent and will pee right on it.
I only trust two Brands: Nok-out, and Anti-icky-Poo. Don't just spray a little on it, really soak the area...
I hope you get this solved... This sounds to me like he might have an UTI...

If he's gotten to spots on the carpet several times your best bet is to pull the carpet back in those areas and check the pad (it'll probably reek of urine) - if it's nasty you need to replace the padding. Two reasons for this 1) it's hard to get urine out of what is essentially a sponge and 2) it's probably started breaking down the pad itself. When the pad breaks down it can mess up the floor below and make the carpet look weird.

Depending on the flooring underneath, paint or seal it after treating it with the enzyme cleaner. If hardwood treat more carefully.

By doing it this way you can completely saturate the pulled back carpet with the enzyme cleaner and it should dry pretty quickly.

7 cats, 3 litter boxes is definitely not enough. When behaviors such as urinating on stove tops, counters, areas that are high ground and obviously unnatural are extreme signs of stress and threat from the other cats.
I hate to say this but you should consider re homing the most recent kitties, no one is happy living like this, especially your cats.

First of all, thank you so so much for being open for receiving help... Yeah, definitely look for Cat Attract Litter - it does an amazing job...

But the first thing you need to do, really, is to take your boy to the vet to rule out an UTI... That needs to be done ASAP.

I buy Anti-Icky-Poo by the gallon at Amazon - here is the link. I am glad you use the storage containers for the litterboxes - IMO those make the best ones!

Hopefully you don't have to replace the carpet, it can be cleaned a lot easier. Though, rather than replacing carpet with more carpet if you ever decide to go down that path - consider tile, laminate, or wood. Easier to clean up and healthier.

Can you stash a couple boxes in the living room and maybe add another box in the spare bedroom or mud room? Even side by side boxes will work as it will give cats more choice and space.

Amazing how you are blowing off all the suggestions that this could be a health issue. Please call your vet and get your cat in to be tested. That is the first step when this type of situation occurs. Once you have ruled out the health issue, then you put your detective hat on and try to figure out why the inappropriate peeing issues are happening.