How can I stop my cats from peeing on our leather couch?

The keep peeing in the sameot. I've cleaned and scrubbed and used cleaning products that are supposed to get rid of urine odor and make them not want to do it again but they still do. It has seeped down inside the couch so I've also sprayed chemicals there. The smell is still faint but I think they keep going because THEY can still smell it. Does anyone know of something to cover the couch so they won't do it and if they did it would be on something washable. We can't use a plastic cover because we have a toddler and fear suffocation. Also, is there a type of couch that is sturdy and washable or something that repels liquids?