Cats keep pooping on the couch!

Luckily it's a couch we hardly use and keep it covered with old sheets since they've developed this new habit. Nothing has changed and we keep their litter boxes spotless. I don't know why they're doing this. I literally just deep cleaned that room (along with the whole house) and bleached their litter boxes to make sure they knew it was clean and they're still doing it. One even peed & pooped in front of the door! I don't know what to do. I love my kitties but if they keep doing this I'm going to have to rehome them. I have a baby that's starting to crawl and I can't have him around that. I really don't want to lose my kitties if I can solve this problem!