Cat Peeing Outside the Litter-box?

My cat, Kida, is a twelve, almost thirteen, year old female cat. I've had her since she was a month old, along with her brother. Both of the cats are strictly indoor cats, and their front nails are clipped. They are both also fixed.

Until 2012, Kida never had any problems going outside of the litter-box. Recently, two of my friends moved in with me. They both take care of the cats when I am away at school, feeding them, giving them fresh water, cleaning their litter-box, etc.

That was when Kida began to pee outside of the litter-box. Sometimes she goes on the floor, but she usually goes (when it is outside of the litter-box) on clothes or towels. The clothes/towels are not mine, rather ones that belong/were used by the other two roommates.

But neither of the roommates do anything to mistreat her; instead they take care of her a great deal. She lets both of them pet her, and she isn't unhappy being around them. She doesn't pee on other fabrics that they have used though, such as blankets that often fall from the couch to the floor.

Also, one time when I was here alone with the cats, she peed on a grocery bag of garbage (that didn't contain fabric). Neither of the new roommates had even touched the bag, so that doesn't make sense with the idea that she dislikes them. The same with peeing on the floor, that is has nothing to do with either of the roommates. There are also similar things left in the floor that she does not pee on, such as grocery bags and pillows.

Despite this, I do believe that her peeing has at least something to do with marking since the two new roommates moved in. However, I do not know what I need to do to fix the problem. The litter-box is cleaned regularly, and even when clean, she will still go outside of it. She usually pees on things she isn't supposed to, when we are in another room or not at home - mainly where we won't catch her in the act.

I just want to know if there is something I can do to fix the problem. The roommates will be here for at the very least another seven months. I also will not get rid of my cat, so I really need to find something to fix, or at least help with, her peeing outside the litter-box.

By Karley G.