Treatment for guinea pig mites (URGENT)?

Hello, well first things first I think my 2 guinea pigs have mite, however my oldest one seems to be experiencing it more harshly than the other, he is an abyssinian guinea<--(my Eldest one) and I can see that his hair has goten alot shorter and it looks dry and fragile. My youngest one I can't see any change apart from that he scratches quite abit. The only problem is that my parents are in denile and don't won't to pay ANY money to go to the vet. So I really can't take them to the vet at all. My parents won't let me :@! I Love my guinea pigs sooo much and really don't want them to p away (as I hear mange mites can be fatal) my youngest guiney ws always quite shy, but my eldest was always really bubbley and active. Now he just slouches around and sits in the corner. He chatters his teeth at me whenever I try and pick him up, and never purrs when i hold him. Hes had this condition for a couple of months now. It's not that bad but very notictable in one particular area.