I have a multipet household and one of my male cats (all are "fixed") is very territorial and will mark territory when feeling the need to show who is boss. For me, it has taken dividing the household into two sections... one where he and those cats he does not have dominance issuses with live and another section where the other cats that "bother" him live. This works mostly because the house has what was once a "mother-in-law" apartment attached which I use for my studio area. He still sometimes will get upset and mark if there are stray animals around that he can see. Interaction between the households is supervised and eventually I hope to unite them but I expect it to take time. I have united households before but I was able to be home more then....

One vet I knew swore that anytime there were more than 7 cats in a household, someone would develop pee-problems, while I have not found that to be true, some cats have a lower tolerance toward changes in the colony.

Can you give Brutus an area that is less crowded? I know some of the other people on PT have used stress-lowering scents and meds... those might help. It sounds like it is might be the outside cats that are triggering the marking. Can you prevent him from seeing them? Can you move their feeding area away from tyhe house so he feels less threatened?

Having a behaviorist evaluate the situation and make suggestions might be good. It is also possible the problem may clear up with the added litterpans and the treatment for the urinary problem....

Good luck. I hope you won't have to find a lower stress home for your Brutus. Good luck!