Your brother by using a condom did not have a risk.
Leg pain has nothing to do with HIV, never has and never will.
I've just read an article about neuropathy. besides ARS pain which occurs only with the other symptoms, how long will it take for a positive person to develop this kind of condition> how many years to be exact?
Talk to a Dr. Your question has nothing to do with a risk assestment. Anxiety of you has nothing to do with HIV.
If your brother had a risk then 3 months is when he can obtain a negative test.
Oh and get off online and stop searching for HIV info, causing yourself more harm over no risk encounters.