Power of Attorney for Joint Holders

Have a ancestral property from my late grandmother now transferred to the legal heirs of her son ( late my father) so the plot is now in joint ownership of my brother, mother and me. We want sell this plot now. My bother is based in Kenya so can't come for registration at the time of sale. So please advise if my brother can give a Power of attorney to me or my mother to sell the plot. Also, kindly confirm as to how do i get the POA done and get it attested. Please confirm process. Thank you