Has your brother already been accepted to a medical school? If not, I can see that it would be quite difficult to persuade a bank to give you a loan. However, my medical school classmates here in British Columbia have not had any difficulty in arranging either student loans via banks, or obtaining lines of credits from the same financial institutions.
The best piece of advice I can give you is to try to contact the medical
schools that your brother is interested in/has been accepted at, and ask them
how the majority of their student's finance their education. I'd bet that
the vast majority of their class relies on some type of bank loan.