If it's being done by a male I would say it's marking. Even at times if they are neutered they will mark if you had let them get those hormones going and had waited to neuter them fairly late. I have heard that females can also be markers.
I feel your pain. That is horrible that they do that on the sofa. I would keep them off of any furniture until they learn to not do that.
__________________  Lulu will always be in my heart  |