1. Since the land mafia is attempting to grab your land you should firstly file a police complaint to the jurisdictional police station to protect your land and then immediately file a civil suit to seek permanent injunction to restrain your brother and land mafia from dispossessing you from the land.
2. If on the online portal the land is seen as transferred to another person then possibly a forged sale deed may already have been executed. Immediately engage a local lawyer to conduct a title search in the office of sub-registrar and if the land has indeed been transferred then file a suit for declaration of the sale deed as illegal.