My parents have a cat that is 5 years old. She was using the cat box fine. Then I moved home with my cat and now she is peeing on the bathroom rugs. Any suggestions on how to get her to stop this is GREATLY appreciated. Thank you in advance

Cats are very territorial.

My two cats will share a litterbox, but only because I got them as kittens together.

Cats introduced as adults are going to have all kinds of issues with each other, sharing a litterbox being one of the larger ones.

Cats also have a whole 'poop and urinate' hierarchy, meaning the litter box is yet another area where one will dominate the other. My female cat Belle, being the alpha, doesn't bury her poop in the litter box, while her much larger brother Zeke not only buries his poop, but will also bury Belle's as well.

This is a dominance thing, and the peeing may be the cats way of asserting her dominance over the other cat, or it may be that the other cat is asserting dominance over the litter box.

First she needs to be vet checked. 80% of inappropriate elimination are UTI (urinary tract infections). However, it sounds like she is just mad. All of the areas MUST be cleaned with an enzmye cleaner. Rehousetraining is a good option. There are several good tools that can help you such as Feliaway and Cat Attract. Try your vets office. If you need more info on how to rehousetrain just let me know. Hope this helps, D