I am sorry to read this but so glad you are looking for ideas to try and you will get very good suggestions here. I will simply repeat a few The one cat box per cat always seemed excessive to me but I have learned it is VERY important, especially to some cats. You might also try using one HUGE box. I have five cats and use three huge rubbermaid containers that hold 40# of litter. Also keep the boxes meticulously clean as some cats are very picky. I prefer clumping litter but even clay litter can be kept clean with care - getting every log & pee biscuit out daily or more often. (Pee biscuit = well, you get it) Keep trying things Sandy and thank you for caring about your brother's kitties. Oh yes and as moosmom mentioned there are some great enzyme cleaners that get even old stain and smells neutralized. I like nature's miracle and used it recently when we had some granddogs visiting.