Landlord & Tennnants issue

Hello Sir, We are residing at gaothan koliwada Mumbai (G+2) structure which is prior to 1960 my father taken possession of room as a tenant (pagadi) an paid 1.5 lac in 1993 to landlord. Now landlords are deceased for more than 10 years. Deceased landlord has 03 Sons & 7 Sister as a legal heirs. After death of mother in yr 2009 we started paying rents to elder son which was 350/- Rs after year he increased rent to 600/- Rs Month from us but no rent receipt were given to us after that some how we have taken in writing that we paid rent from 2014 to Jan 2020 on plain paper with proper revenue stamp & signature of elder son dated 01.09.2020 receipt. For past 20 year no bldg repair work maintenance done So BMC gave Audit notice & after that 351 notice as illegal structure to owner/ occupants Audit report stated C2 category we inform elder son to tk steps bt we replied to bmc notice and request elder son to carry repair work. Now last week UN-sudden 2nd son & sisters came up and schedule meeting with tenants he told now am handling bldg affairs POA will be given to him from other heirs & new construction will be carry out with official permission. you need to pay 20 lac each etc. He has given us 7 days to tk decision on it and ask us to hand over copies tenant rent receipts, agreement & ID proofs. Question is 1. Our Rent is paid up-to Jan 2020 now elder son is not taking rent from us he told us that other brother is handling all affairs Now what to do ? 2. We have rent receipts with us and we have agreement bt not in our hand. if it is oral is there any problem? 3. For last 10 yr elder son used to tk double rent & we have taken acknowledge of payment of rent [deleted] from elder son with revenue stamp and signature on it as well requested to let us know formula of rent increased official assessment & water bill come up-to 3000/- Rs Pa and taken amount 7200/- Rs Pa from us is it valid? 4. Shall we give copy of documents to 2nd son document such rent receipt & agreement without any concern from other brother or POA Requested to let me know what to do elder son has pull his hand up & now told orally his brother will look bt no letter or intimation given to us ask us to come mira road for meeting plz advice sir a