Stinker- does that mean he stinks from the mouth? This could be not only kidney stones but even kidney failure?

Kidney stones: young cats of some years can have that too. It means that he should only get diet food. Whenever he has a hard time peeing he has to see the vet immediately as a cat can die when he is blocked.

The vet should also be able to say whether the teeth need cleaning. This can occur in cats that are as young as 2 years. It is the same as with humans: some cats have more substances in their saliva that builds tartar on the teeth than others. If it is not treated, the cats are in pain and they can loose their teeth.

Good luck with finding out what is wrong with your brother's cat.