If only we could understand why kitties do this! You have two litter boxes, which is great, lots of cat trees. If this is a jealousy thing .... then that has to be solved. There should be room on your lap for both of them. LOL. The whole peeing outside the litter box is so aggravating and once a new place is used, Jackson Galaxy recommends putting a litter box there (a new one). Cats really prefer a litter box. You might want to try
http://www.spiritessences.com and see if they have something you might be able to use. These are holistic remedies that Jackson Galaxy sells and maybe there is one that might work for you. Good luck!