So it seem the main problem now is you login multiple account in one ip and if i am the admin on that site,i also will think that you is referring yourself by making multiple account and bet for earning comission.This problem is totally hard to be resolve without a valid proof.
I don't think you can provide any kind of valid proofs for this case. He can just say opened or operated for other friends but how to believe those things. I don't think for this case FJ will refund him any money or even bother to reply all his questions.