If not for the fluffy fur, Precious is tiny. I am guessing that he may be about two months old or less. Junior likes to play with Precious as if it was one of his soft toys. When he becomes overly rough, the poor little fella will let out a cry and run for shelter.
I only limit the contact time for both kittens to 30 minutes. After that it is back to their respective Pet Condos. Hopefully when Precious grows bigger in size he will be more able to defend himself. And perhaps by then, Junior will be one and would become more mature.