How many litter trays do you have? The general rule is One per cat, plus one. You need to be super meticulous cleaning it up, check out this site to see how http://www.celiahaddon.co.uk/pet%20problems/cats/clean-up.html.
One of our boys is peeing everywhere he's a neutered 5yo rescue boy who came to us in June, along with his best buddy. They settled immediately with no incidents but over the last few days one is peeing everywhere, and blatantly too.
We don't have a cat flap so they can't be tormented in their own home. Dd tries to maul them (she's 13 months) but they go back for cuddles rather than running away.
Problem is, where one pees the other one does too!
Would a Feliway help? And what will help get rid of the smell? I fear I'm going to have to shampoo the carpets