Roger Penrose, Physicist

has a brother named Jonathan who is a correspondence chess grandmaster.

What do you think are the chances he plays here? If not, do you think we could get him to?

Unlikely, I dont know if he is still alive - he would be very old by now if he was still active. He was British champion quite a few times back in the 60s.
I have a feeling if any cgrand master played here he would be noticed quite quickly as he would climb towards 2500 at a rapid rate