My mum and dads boy kitten keeps peeing in there bed and they don't know what to do to stop him, any suggestions?

Would really help.

Well, most likely, because its hard to get all the urine out of a bed (or anything) the kitten can smell its urine there and will continue to do it.

Put the kitten into the litterbox and make it scratch with its paws (use your hand to make it dig) repeat this MANY times during the day. Next, close the bedroom door and do NOT let it in there.

How old is the kitten?
It could be a UTI and he needs medication.
It could be a sign of dominance and it would be hepful to have him neutered if he is old enough. Regardless a vet checkup would be the way to start to solve the problem.

My cat does this and we found out why it's the duvet its plush and rhey can pad and scratch on the duvet and bed so they pee on it.if you change the thick duvet to a big,soft blanket and he should stop