I have redevelopment n release deed related question

Our society is going under redevelopment. After dad ' death , we three siblings and my mom have equal share in property. Cos dad din leave any will written on mom's name. Now since society is going under redevelopment, chairman of society told one shud be holder of flat. Now to make my mom holder of flat. We need to do release deed. For release deed we are ready to give up our shares to mom. But the problem is my brother stays in Scotland. Earlier he told he is ready to give. He sent signed papers through watsup of poa ( power of attorney) To sign on his behalf since he can't come. But now lawyer is saying that pdf of poa signed won't be valid. Need attested embassy poa. But brother is saying he don't have time to go embassy. He says he will come wen he has time But since time n days are passing by and chairman is saying we won't be able to get to sign da agreement and won't get rent. And corpus fund. Now my tension is wat options I have.