) i presume room in chawl was in name of deceased mother
2)if so on her demise your father and aunt would have equal share in the SRA flat
3) if on other hand rent receipts of chawl were in your father name on redevelopment of chalw your aunt would not have any share in said flat
4) if any payment is made by father aunt should execute sale deed wherein she transfers her 50 per cent share in favour of your father