As we females are all to aware some boys(i've found with our lot) are just plane lazy and mardy, or it could be your other lad stressing him for whatever reason. Maybe try 2 litter trays and see how they get on,at this age they are becoming young males as opposed to kittens(even though they are,to us at least) so it could be a dominance issue-the one using the tray all the time being the dominant. Are they neutered? Good luck Annie and do let us know what you try and how you and they get on I say this because it's not always a lazy issue-honestly)If your cat is blatantly dumping/weeing in front of you it's a fair betting he's unhappy about something and this is the plan of action he can come up with to tell youOr if neither are neutered it could be that he's spraying because his body is sexually frustrated but being a kitt his head just thinks he needs to go.