First, get him neutered ASAP! While he's being neutered the vet can check and make sure he doesn't have any urinary infections going on.

Next, if you have only one litter box, add 2 more. You may also want to try a different cat litter since cats can be picky about their litter.

I'm more concerned about the older cat and what the added stress may do to her. She could easily end up with health issues and she may have one now since you never see her. I would try to give her an area or room all to herself so she can relax and return to her 'normal' life. You need to watch her carefully and make sure she is not ill.
Is your house large enough that you can isolate the male to a room with his own litter box for a few days?

Forget air freshener and buy one of the many enzymes made for cat urine (at pet stores) You need to treat every area that he has peed on since he will continue to go back there as long as he can smell it.

ANd while it's true that neutering doesn't always stop these sorts of problems, it often DOES! Are you sure this guy is 6 months? These behaviors sound like those of an older cat. Have his testicles appeared yet? As soon as those start to form it's time to have him snipped! How long have you had him? Whenever I introduce a new kitten (i've never tried bringing in one older than 3 months) I always keep them in a separate room for a few days, then let them met the old cat thru a door, and gradually introduce them. If your old baby is very timid, keeping them completely separate may be your only option.

How were the cats introduced? Did you just bring the new one in without isolating it for a period of time?

I'd make an appointment to have him neutered right away and when he came home, I'd put him in an isolation room and reintroduce the two of them slowly (two weeks at least since the older cat is so tweaked out). Keep his litter box in his room and this way you can make sure his inappropriate elimination has stopped. Once and awhile you'll get a cat that wants to pee in one box and poo in a second one, so keep that in the back of your mind, too. I think that 6 months is too old to not be fixed in a house with another cat, but that's just my feelings. Why invite this kind of trouble? It's just awful when they don't use the potty box.

You're going to have to get rid of the elimination odors with enzyme cleaner as was suggested above. Air fresheners don't kill the scent and the cat will continue to keep marking his territory.

You should have at least 2 clean litter boxes if you are having a problems, 3 if you have the room. I keep 2 side-by-side in my basement and it works out just fine for my 2 cats.

you've been given some great advice above. Definitely get him sterilised as often this does stop these types of behaviour especially when you get them snipped young and they haven't yet formed these behaviours into habits, and you don't want him spraying in the house either. They need to have separate litter trays, and put them in a couple of different locations. Sometimes cats do not like sharing trays, some cats also need their tray to be spotless or they just won't use it so you have to give them more options then sharing one tray.

The advice about introducing them slowly above is also good, even dogs can have trouble adjusting to a new dog, and cats are much less social animals with each other so introduce them while you supervise, and until they get to accept each other, you may have to separate them for some of the time but do it gradually, cats don't like sudden changes in their environment and for both of them, learning to live with each other is a very big deal.

Annz covered most everything I was thinking precisely, and probably a lot less wordier than I would have. Definitely get him neutered ASAP.

My youngest cat was only 4 months old last Christmas, and he was a terror much like your guy is. Though he doesn't have elimination issues, he does have a lot of aggression issues. Also like you, he is just a doll with my young child- they are attached at the hip and that is a major redeeming quality IMO.

We did a lot of gentle discipline with bad behaviors. I like squirt bottles for some of the more moderate behaviors- like when he is clawing at the edges of the carpet, and I like time-outs for the more out of control behavior like aggression. Our boy was very bad last year about attacking the other cat, or even people, and he'd just be so worked up that he couldn't seem to stop himself. In this situation, any of this behavior was an automatic deal breaker and he got an immediate time out. Time out is just being put in a nice bedroom, that does have cat amenities, but it doesn't have interaction or attention. I would put him in the room alone for 15-20 minutes, then let him out, and if the aggression started back up, he immediately went back in for another 15-20. Maturity and discipline have made him a much better cat than he was a year ago, nowadays if he goes into one of his out of control modes, he is fine after a very short time out.

I would like to think that this would work with his aggression toward the other cat- and that the other cat will learn the outcome as well, and probably like it. If you were to put him in a time out at the first attack of the older cat, he will soon learn that the behavior gets him nowhere except alone- and the older cat will probably start baiting him to get the reaction (I swear my old girl will do this sometimes).

At first it will probably seem like you are constantly correcting, but things will change given time. We still have issues with our guy, but thinking back to last year- and how he destroyed the Christmas tree- we can see how far he has come.

This year we have been using apple cider vinegar under and around our Christmas tree, and it has seemed to deter him for a few days at a time. Initially we sprayed the tree (before it was decorated), but subsequently we have put a sponge in a plastic container and soaked the sponge with the vinegar, then set it under the tree. That might help him stay away from areas that he seems to like, but as has been noted, you need to thoroughly clean up any marked spots with an enzyme cleaner to make sure he cannot smell that this is an area to be marked. Citrus spray did nothing to deter our cat from getting anywhere near the tree- we just had a citrus fresh kitty throughout the holidays.

Our cat also has much better behavior if he is exercised heavily each day. DH runs him around with a laser pointer every night before bed, and if we miss doing that even one day, the next day he is much more wound up. The major issue for us with the laser pointer is that our child wants to do it too, and you need to be careful that those things don't get pointed at cat or people eyes. She is pretty good about understanding that only Dad or Mom can do the laser pointer, but sometimes she can get him to chase the light of a regular little flashlight too.

Good luck to you. I know how frustrating it can be to get a wild and crazy guy.

Getting him neutered in about a week. I didn't know anything about neutering so soon. Our vet and vet friends told us around the six month mark, well it's been just about that time maybe we should have done it sooner. What you said makes sense about getting it done before habits start.

Just the other night my wife was folding our son's baby clothes and putting them in a basket, the cat jumped in the basket and about five seconds later he had sprayed/peed in the box. Now he meows a lot more and I think he attacks our son's crib because he woke up the other night screaming and standing up in his crib.

I use Nature's Miracle but he still seems to want to go on the xmas tree skirt, even though I sprayed all over it. I bought the never mark one but I didn't buy the one especially for cats since the ingredients were practically the same for the general kind.

I'm sure this will be a futile effort especially at this point. I am willing to bet he will get neutered and continue his behaviors to the point of us posting on craigslist or driving to the shelter.

I think you'll be quite surprised once he's been neutered. He's basically reaching sexual maturity so his body is telling him to be more aggressive, spray and mark his territory etc and be dominant over other cats, but once they get snipped it usually does shut down their hormonal behaviours that in a male cat especially can be a real problem. His body won't be sending him those signals that create the behaviours and males can change quite a bit once the hormones aren't driving their behaviour so getting them done young is really the best way to go. He's actually not being a bad cat so much, as a typical hormonal male cat.

please let us know how it goes

Just be aware that it takes a while to get all the hormones out of his system.

Here is a link that might be useful: Google search

If he was my cat I would also separate him right now, and start re-introducing him once he's been neutered. Give your older cat a chance to build up her confidence again so she feels safe in the house, then slowly start bringing the male back in, if he gets aggressive, separate him for a little while. Right now he's running amok with hormones raging and making everyone's life difficult so he does need to learn some boundaries as well as getting sterilized. separating an aggressive cat is really the most effective way I've found to teach them, if you get angry or scold them etc it often just riles them up more, but if you put them on their own they calm down and start to realise, hey I don't want be in here on my own I want to part of things and they do learn that acting up = being separated, alone and bored.

The last sentence of your last post made me feel sad- it sounds like you have already given up on him? Perhaps you were just having a bad day with him?

Please give him a chance and make the effort, especially for your child who sounds bonded to him. I agree 100% with trancegemini about how riled up cats can get if you get angry or try to scold them. That was definitely true of my guy, if you try to physically stop his behaviors even in a gentle way, he just gets more out of control- time out is the only thing that works for him.

A year ago, I did not know how I was going to survive this cat. He would physically attack me when I had my back turned- he would jump me and no matter how many times I took him off, he'd come right back for me. If I leaned down to talk to him, he'd rush me and start swinging at my face very aggressively with his paws. At one point I decided that rather than a squirt bottle, I would use a plastic shampoo type bottle filled with water and super-soak him to make my point. When he jumped me, I was ready and we both got completely soaked- it did not phase him, he came right back for me.

Now I look back a year later, and while he's still got some quirks, he is a much calmer cat, just with age. Most of his aggressive behaviors subsided around 1 year. Neutering helped him, but maturing and becoming an adult cat has been the key with him- plus enforcing the time out rule for misbehavior.

I sometimes watch that show "It's Me or the Dog" and one of my favorite pieces of advice she gives is to set the animal up for success. In other words, control the situation so the bad behaviors can't exist, and then let them know they are good. While my boy is mostly a good boy these days, he still seems to want to jump me when I am at the bathroom sink. Instead of tempting fate and allowing the situation to escalate, I now just lock him out of the room when I am in there.

I hope you will make the effort with your cat. I think your time and patience now will pay off tenfold later.