Honestly, your brother did a wonderful job by selling the bitcoin. He already tripled his money, it's enough! Look at the market now, BTC price is falling down! Yesterday it was going to hit 14K USD, and now BTC seems going under 10K USD! If BTC price bounces back again at 15K USD, your brother should not be regret, because he has tripled money from his investment. This is not the right time to invest in Bitcoin, the bear market was! Yesterday I sold mine and now I am holding 20%! I will buy again when BTC price comes down!