Registeration of old unregistered property

Dear Sir, The house/property in which I stay was purchased by my grandfather in 1985 from the builder in Mumbai and no stamp duty was paid and the property was not registered at that time. My grandfather has 4 sons and 4 daughters. My grandfather died in 1991 and my grandmother died in 2001. After a long dispute between the brothers, the house was transferred in the name of 2 brothers (my father and my uncle)(other 2 brothers have their own property) after execution of the required documents and to the satisfaction of the housing society. The house is now in the name of 2 bothers in the society records and share certificate. As per the terms between the 2 brothers, my father has to pay him some amount and once that amount is paid in full, the house will be owned completely by my father on execution of proper documents. Also as mentioned earlier the property is not registered and stamp duty is not paid. I have doubts with regards to paying stamp duty and registration the property- whether to pay now or later. I have the following query: 1. Option1: Should I pay the stamp duty now and register property in name of 2 brothers. Once the payment (as decided between my father and uncle) is made in full to my uncle, he will gift his share to my father by executing and registering a gift deed. 2. Option 2: Once the payment is made in full, my uncle will execute a gift deed in favour on my father gifting his share in the property. After that I will pay the stamp duty and register the property in name of my father. 3. Any other simple and better alternative available to my father. Thanks in advance