I was thinking about your kitteh problem last night, and I think Rayne is just too little to be marking his territory yet. Maybe he just needs a little extra reinforcement of the litter box rules. Show him the wet spot on your bed (of course not in an angry way, but in a firm way) say "No", and place him in the litterbox, then gently move his front paws back and forth in a digging motion.
Some kittens need a little more time to remember to go in the litterbox. Then everytime you happen to see that he did use the box, give him extra praises, pets, and kissies. I'm sure you've done all this already, but keep doing it with this kittie until he gets it. I bet my watch and warrant that this will work.
I've had so many cats all my life, and no two are alike in the way they do anything.
Your cats look nice and proud, but I'm madly in love with Sophie! Can I adopt your dog? Well, as I was telling you, "our" furball Sophie is fantastic! Draga says hello to her!. And yes, I was thinking that she looked like Lassie and it's true! a Lassie more colorful! Wow! -literally, LOL!-