Handing over of vacant possession of Office property

In 2003, we had entered into Lease for our Office of area around 2000 sq.ft. The owner had assigned his wife, son, daughter and daughter-in-law as the Lessors apart from himself & some of his Companies and we signed 8 Lease Agreements with part monthly rents to be paid to each. The Lease was not registered. Subsequently, two portions were sold to a third party and based on letters exchanged, the rentals for those 2 portions were paid to the new owners. In the meanwhile, there were family disputes with the father, the owner on one side and the wife, son & daughter-in-law on the other side. Then the father demanded that the complete rent to him or to his assigned companies. As a via-media, for those disputed portions, we split the rent on 50:50 basis to satisfy both the parties. Now we wish to vacate. The father, who claims to be the sole owner, wants us to handover the possession to him where was the other side demand to be given to them as they are the Lessors. What to do?