Serious urinary problem

Hi, I moved in with a roommate a few months ago. I brought with me my 2 female cats and she brought with her a male cat. All cats are spayed. In the beginning my 2 female cats have been intimidating my roommates male cat. I believe the tables have turned and now the male cat seems to be intimidating my female cats. The problem is that my female cats (I think it's one in particular) that is urinating, I think marking her territory in my roommates sons room all over his belongings. This is where the male cat hangs out alot and is protective of the little boy. I have replaced his belongings. The flooring is pergo and we have cleaned it up and poured vinegar over the areas. But the cat keeps on going back to the same place and urinating all over the little boys belongings again. I don't know what to do, except get rid of the cats, which I don't want to do but this can't continue on. Please any advice would be appreciated - Thanks