Landlord brother sent notices to tenent

Party 1 Is the tenent of party 2, party 1 gives rent for 3 shop regularly & party 2 also given rent receipt regularly from 20 yrs . Party 2 elder brother send notice to party 1 & his younger brother party 1 , that the shop are in prime location then he want share in the rent and want more rent , but there is no name of the elder brother of party 2 in the rent receipt & electric bill , and party 1have lost the agreement copy in the major fire took place at party 1 shop 3 yrs ago Pls suggest what should party 1 replay of party 2 elders brother notice send by his advocate