Transfer of Tenancy rights as per Pagadi system

My mother in law staying in the Padadi system house at Chira Bajaar right from her birth ( even after her marriage) but after her father death the rent receipt of the property is been transferred to her Brothers name however the rent is been paid by the her son from his accounts since we all are residing there. Now her brother is willing to transfer the tenancy right to her name but he demanded around 15lac rs. her son have already paid Rs 9 Lac & said the balance will be paid once the landlord does the transfer work complete. but landlord his taking his own sweet time & purposefully not paying attention to this transfer from brother to sister's name. & only giving assurance that this will be done soon. meanwhile her brother is asking for the balance Rs 6 lacs from her in this situation we are not able to decide anything weather we pay the balance money to her brother if yes then what documentation we should keep it ready till the time landlord does not initiate the transfer process to keep the proof of money paid. kindly advise