My cat keeps pooping on my floor!!!?

i have 3 very wonderful kitties names hoeboe myew and sushi. heboe wont stop pooping on my fool myew and sushi (my 2 girls) go to the litter box but hoeboe wont. i can deal with this nasty habit of his any longer i need to know how to fix this and or y he is doing it he is neutered and sushi is spayed but myew is not but i dont thing that it would be about my little one being spayed because hoeboes neutered?? i need help