Widow wife of sibling refusing to co-operate to dispose-off the flat claiming possession

Sirs, Our father owned one 2-bhk flat in Mumbai. He died intestate in 1971. We are 8-Siblings. 4 brothers (B1, B2, B3 and B4) and 4 sisters (S1, S2, S3 and S4). All married except S4. At present the flat is occupied by widow (W1) of B1 and their daughter (D1) along with S2 (divorcee). The rest of the siblings are living separately. Recently, B1 too died intestate in Feb’20. It was proposed by the siblings to sell the flat and distribute the shares amongst siblings. But W1 + D1 are refusing to co-operate. What are the various remedies available to us siblings?