Cat problems

[StarWolf]

I've had my cat(Mirage) ever since she was a newborn. I saw her born, and was with her and her littermates and mother as she grew. We took her home and I found that we didn't even need to really train her to use the litterbox- I simply took her there every half hour for the first 2 days and after that, everything was perfectly fine.
Now Mirage is a two year old cat(But she still is pretty small and acts like a kitten, so I refer to her as a kitten) and has begun to use the bathroom(Both poop and pee) outside of the litterbox. Her litterbox is in the downstairs bathroom(Our house has two stories, but there isn't any room upstairs for another litterbox) and we feed her in the utility room, which is across from the downstairs bathroom. We feed our cats two times a day- Axel in the bathroom, and Mirage in the utility room. Mirage isn't fixed(Axel is, though) and has never had this problem before. Nothing has recently happened, and she was perfectly fine with the types of litter we had before, and she never goes outside. We have found pee and poo both in the bathroom(Which is where it was at first- just outside the litterbox, and not inside it) as well as the living room(Which is also near the bathroom).
If she doesn't stop, my parents said we have to get rid of her- I really don't want her to go, so does anyone have any tips on how I can get my cat to use the litterbox again or why she is even doing this?

EDIT: I am gonna add any and all suggestions/tips to a list, that way it's more organized for me.

[kimiko70714]

Have you had Axel since before you got Mirage, or is s/he new? If s/he's new, the scent of his/her droppings could be upsetting Mirage's normal behavior. My suggestion is to get another litter box and put it in the [insert room of house where it can go] and then re-train Mirage to use it instead, by using a scoop or plastic bag to move her droppings in it- she'll get the idea that she should go there instead. That's what I had to do with my foxes and they behave just like a cat, so it might work.

[StarWolf]

We've had Axel(the tomcat) for 3-4 years now, back when we also had Angie(Mirage never knew her). Then I got Mirage(the she-cat), so they've been together for over one and a half years.
And I'll try that, if I can get my parents to get another litterbox(the one we have and have had for a while is hooded, so should the second one be covered or no?)

[kimiko70714]

We've had Axel(the tomcat) for 3-4 years now, back when we also had Angie(Mirage never knew her). Then I got Mirage(the she-cat), so they've been together for over one and a half years.
And I'll try that, if I can get my parents to get another litterbox(the one we have and have had for a while is hooded, so should the second one be covered or no?)

I don't think it would matted if it's hooded or not... And I don't really know why she'd be doing this if both have been together for a while.

[NatureHeart]

Is her litterbox in plain sight? Cats like privacy when they go. (It doesn't matter to some)

[StarWolf]

Well, it's not hidden, but it's not like.. in the center of a room. When you walk through the bathroom door, the litterbox is directly to the left- so it's between a wall and sink. Plus it's covered. We just added another litterbox(to see if you really need 2 boxes for 2 cats) but she didn't use it... I watched her for a few hours and made sure she went to the bathroom in one of the boxes. She checked out the newer one, dug around a bit, then went to the covered one and did her business.
Weird cat. ._.


EDIT:
A mod can lock this topic. My parents are getting rid of her. Thanks to those who tried to help.