Are male cats more aggressive, spray, or harder to litter train?

I'm sorry you're having this situation!  It increases the stress for everyone when inter-cat relationships are aggressive.   While uncommon in neutered males, sexual aggression is still possible. Here is an interesting article from Tufts university regarding this issue.     I haven't personally run into this in my practice, but I have heard of Boar Mate spray being recommended.  Sometimes anti-anxiety medication such as fluoxetine can also be helpful when given to the aggressive cat.   Talk to your veterinarian about specific recommendations for use. http://www.tuftscatnip.com/issues/22_1/feature/Understanding-Feline-Sexual-Aggression-222-1.html

She probably wants to go outside and has had a change in attitude because she is becoming sexually mature. If you are not planning on breeding her then she should be spayed (sterilized). This will probably stop all these unwanted behaviors.

Male cats will reach sexual maturity anytime after six months of age. They will want to roam more, can and do start fighting with each other and other cats for females and territory, and will urine mark their territory. This will include spraying it the house, which smells terrible and is almost impossible to get out. They can also become more aggressive. Unfortunately there is nothing you can do about these behaviors, the only way to prevent them from happening is to have them neutered. If you don't want to do that, then you will have to understand that they can and will mark with urine in your home, they can be gone for days roaming around, and they will be more prone to fights and therefore injuries. It truly is better to have them neutered for their health and behavior, as well as for your home. I hope this helps!

Thank you for submitting your question regarding Axel. He has not gone through puberty being only 9 weeks of age. Therefore, this issue is likely related to not being fully potty trained yet as opposed to marking behavior. You can add another litterbox and make sure it has a very low lip to make it easy for the kitten to get in and out. You can try another litter substrate to see if he has a preference. Finally, wash your bedding and do not allow him access to it. I hope this information helps!

It is possible. Ideally, in a multi-cat household you should have one litterbox per cat plus an additional litterbox in a neutral area. Try sprinkling a litterbox attractant in the box to entice him back. You can also use a pheromone product, such as Feliway Spray or plug in diffuser, to help decrease any anxiety associated with the new addition.

Unfortunately it is extremely difficult if not impossible to train a male cat to ignore the natural instincts, such as urine marking, which make them difficult to keep indoor. Male cat urine has an extremely strong odor, and is quite unpleasant, and it's their natural tendency to "mark" areas that they consider to be theirs, which in your case will likely be all around the inside of your house. He will also be very interested in leaving your house to roam in search of females, and to fight other males that he considers to be a threat. Clearly, these are dangerous behaviors. While you may be concerned about the safety of neutering, since it requires general anesthesia, I can tell you that it is a well-understood procedure that is nearly painless, and takes no more than 5 minutes if performed by a trained veterinarian. Once DoReMi is neutered, he will no longer have the "urges" that drive the behaviors listed above, and will be quite content. I strongly advise you to have him neutered, and soon, as he's getting very close to starting to become sexually mature.

Good question. Yes he has a good chance at spraying in the house if you bring in the intact kitty. He also has a chance at spraying if you don't. Cats are very unpredictable in this regard, and you also have to consider any stray cats in your area that could trigger Lucifer to start spraying as well. I would recommend neutering him soon if you want to prevent this from happening, because the chances that it will happen before he turns 1 year of age are high regardless of what you do.