Old cat kicked out of bedroom for new kitten, cause of anxiety?

Question

We just got a new kitten and have been keeping her in our bedroom. Now our older cat cries at the bedroom door wanting to get in. He’s anxious and pacing because there’s a closed door. But we can’t let him inside because he will eat the kitten’s food and harass her. He spends all day outside the bedroom door crying and scratching, whether we’re in there or not.

We’ve tried a slow introduction, but when we got to the scent swapping step, all the older cat wants to do is search for the kitten’s food, and then look for her. If he can’t find her, he pees in the closet where she naps.

We’ve tried both felaway defusers, so many litter boxes around the house, and medicines, but the older cat still paces and urinates outside the litter box, presumably due to his anxiety. We’ve gone to the vet countless times with our older cat but there’s nothing physically wrong with him.

What can we do to make everyone happy and less stressed?

Edit: our male cat is neutered and so is the female kitten. I neglected to mention that the male cat has a litter mate that he’s lived with his whole life. He’s no stranger to other cats in the house. We actually got him and his brother at the same time when we already had an older cat in the house. So this is the second time he’s been in a 3-cat household, but the first where he’s been not allowed full reign of the rooms.

Second edit: there also has been some additional change in his life (I know cats don’t do well with that).

We’ve recently moved (he was anxious before the move 4 months ago), and we’re expecting our first baby, which means new furniture too.

Answer 1

Your older cat is male. If he isn't neutered, the chances that he will ever accept another cat in his territory are very slim. Male cats aren't very social creatures and usually choose not to live together with other cats.

In your special situation, the male cat has lived alone and has claimed the whole house as his territory. Now there's a new cat that he perceives as an intruder. If both cats were adopted at the same time, the situation would be different, but now there is no way how the new cat couldn't intrude on the old cat's territory.

Especially the peeing in the place where the kitten usually sleeps is a sign of dominance and territorial behavior. He is claiming the place as his by marking it with his scent. He might stop burying his poop in cat litter for the same reason: to assert his dominance by spreading his scent. You need to watch over him or he might get into the habit of marking walls and furniture with urine. This is also a problem that is solved by neutering the cat.

You should take the introduction very slow and not allow both cats in the same room, otherwise the older cat might attack the younger one.