Transfer of property on the basis of Unregistered Will

My Father in Law has prepared his will for his property in Delhi. The Property has Ground Floor, 1st Floor and 2nd Floor. Will in respect of 1st Floor was in my favour (Elder Daughter-in-Law), 2nd Floor is in favour of younger Daughter -in Law (wife of my husband's brother), Ground Floor in favour of my Mother - in - Law. After the death of my Mother-in-Law the Ground Floor rights will be shared between my husband and my brother -in-law. It was witnessed by two people. My Father-in-Law died in 2007 and the will was not registered in the Court. My Husband (his elder son) also died in 2010 and the property is still not transferred in anyone's name. My Husband has two sisters, one is in US and one is in Delhi. I have two sons. I need to get this property transferred according to the will. Pls advise 1. if the NOC from Sisters is required from my husband's sisters. 2. In case of death of my husband, whether my rights are their on this property or both my sons have rights on this property. 3. What would be procedure for probat, if required.