The PAN card is also a valid identity proof replacing AADHAR card. She can give the copy of her passport too additionally. If you want to give power of attorney to your brother he can act only on your behalf if you want your wife to relinquish her rights in the property by executing a registered release deed.
However you both can execute a POA deed duly attested by an official of the Indian consult of your country of residence in favor of your brother authorising him to sell the property on behalf of both of you.