Need help majorly!!

I have a 5 year old black bomba male who has a neorglocagial disorder where when he gets upset or scared he shakes a lot till he can get calmed down, the problem is that 4 months ago my sister, her boyfriend and his son with their 1 dog all moved in and he got upset and not at first but in the last 2 months he started to pee in the vents and on the kitchen floor. I have had him to the vet and the vet said he is very healthy and this is a behavioral issue. I dont want to have to give him up for he is my baby, but i also would love to not have to keep him lock up in my room while im away at work, i will take any advise and give it a try, please help a cat mom save her baby

Have you gone through any process of helping him bond with the new people? Even as a human, if strange people moved in with me and I wasn't much consulted, I probably wouldn't get along with them.

Thats a new idea, thank you, but it might be hard when i have heard my sister even say she doesnt like cats inside which all of my cats are

You can get magnetic vent covers that may make it more difficult for him to urinate in them. Confining him to one room while you're away can be helpful as cats often cope better in a smaller space. Using Feliway, a pheromone spray which is made for calming cats down can help as well.

Thank you