Peeing on blankets

Hello! I have a 1 1/2 year old spayed female and a 1 year old nwutered male bunny. my Male is peeing on anything soft I put in the cage I don't think it is illness, more than likely behavior since he literally will run right to a new blanket and pee on it. While running in the house we have no issues because we have all hardwood, but I like to keep a soft bed for then inside their crate. Is there any option other than just not giving them anything soft????
....they have been bonded for 6 months, no environmental changes, diet changes, etc.

You'll have to experiment with different options. A bath mat, a cat bed, a rug, a doormat... any of these may or may not work as alternatives.

Another possible consideration is seeing that their current litter box is plenty large. It should be large enough that they could both stretch out in there together (size-wise -- not that I'm encouraging them to do so).

had the same problem with Mr.Peter Bear my flemish. after a while, he stopped and started fully peeing in the box

He may be marking his territory on the blanket, if it is a new one. If the female uses it as well, he may smell her scent on it and want to make it clear that it's his blanket. Try getting two seperate blankets for them to use so that he doesn't feel the need to mark his territory. Keeping the blanket in there would be ideal in order to prevent them from getting sore hocks from sitting on one platform for to long. I hope I helped!