Property rights for 1st wife son

Dear Sir, I'm an Hindu . Mine is joint family. In the year1987 my father decided to purchase a property measuring 18×30 out house. But my father was a govt servant along with that he had 2 wifes ( own sister's ) 1st wife younger sister with 2 children's one daughter and one son and 2nd wife last sister with one son.we are all leaving together till date. My father decided to register the property in 2nd wifes name because of the following reasons- ● my father's second wife was at govt service and my father was near to retire . ● as per the govt rules my father is not allowed to have 2nd wife when 1st wife is alive. ● my father borrowed loan from hdfc in 2nd wifes name . my father registered the property on 2nd wifes name after taking consult from all my family members. as per the above reasons. My father paid installments every month from his salary after drawing the amount from the bank and paid installments on time for more than 9years for that I have bank and deposit slip proof. Unfortunately my father expired on jan 2010 , later the remaining last 4 months installments was cleared by my 1st mother and my second mother. In 2015 1st wife expired, and in 2018 2nd wife expired. Know my father and his both wifes are expired. But the property is still in my father's 2nd wife name . I 1st wife son and daughter informed my 2nd wifes son to change khatha into joint khatha and leave together, but my brother of 2nd wifes is not accepting to change khatha to joint khatha. Know my question 1st wife son and Daughter has right on property? Till date we are joint family members. My father paid from bank account to installments. Please help me in this Ravi Unfortunately my