Kitten pee problem... help

I have three cats, all two years old and under, and all are inside only. My youngest kitten, who is a little over a year old, will not pee in our litterbox. She will do her other business in there, but will not pee. Instead she resorts to peeing in corners around the house. She is very secretive about doing it, we rarely catch her. And when we do see her in the litterbox, she acts embarassed, jumps out, and runs away.

She gets along ok with the other cats, they do not terrorize her or anything like that, just normal playing and play-fighting. If anything, she picks on them more than the other way around.

Our litterbox is spacious and cleaned very often. We've tried sprays to ward her away from corners but it doesn't help, she just goes back to peeing in the same spots.

How can we get her to use the litterbox like the others? Any advice would be greatly appreciated.

Definitely get at least one other box. Many cats won't 'go' where others have been and you should have at least one box per cat, if not more. A nuisance, but it works. Try putting one small one (small for now and as a deterrent to others) in a place she's likely to 'use'. Stand her in it, 'walk' her forepaws a couple of times on top (she'll get it right away) and then leave her alone. And cross your fingers!