Minority Registration & Gift deed cancellation

Hello sir, We have a problem with property will registered by my wife's Grand Mother. She got that property from her husband who has passed away by the time of Will registration. She has two Daughters and one son. None of the daughters were interested in the property as they got their share at the time of their marriage. The son i.e., my father in law has also expired before the time of Will registrations. My father in law has four daughters in which 2 of them were minors and 1 unmarried dependent at the time of registration. Only elder daughter got married after one year of my father in law got expired. Due to some financial problems took some amount from their son in law, later for the debt he asked them to give him half of the property i.e., site As they didn’t find any other way they accepted for it and in registration it was mentioned like as it was a gift deed so that the percentage of stamp duty that he need to pay will be reduced, but now after 8 years the issue got raised up. Because after that he settled in the top floor by constructing a half completed house with a roof which my mother in law would not like to do, but he didn't bother he settled there without any rent for that he is saying as i invested in constructing so i have the right to stay and my mother in law also took an amount for their 2 daughters marriages. He told that it was for less interest. My mother in law also accepted but after that she could not pay he went go on increasing and now it became a huge amount. And he also enjoying the property by taking the rents in that site (An old 4 storied house in that site) he got through the gift deed, and staying in their top floor without rent & collecting interests for the debt. After I got married with their third daughter came to know he is cheating them in all the ways which was not realised by mother in law. So I & second daughter’s husband gave a notice to them that the registration is not valid as it is not distributed equally (As grandmother gave half of the property to her elder granddaughter) & a minor(my wife) was signed as a major. My mother in law sends a caveat to us with that first daughter’s husband. After that she came to know that he is asking for both the land and the share in the house. Later we didn't move further as my wife & her sister not interested to go court and tried to settle out side. But they didn't cooperate with us and keep saying them both site & top floor after taking some amount also. After failing so many negotiations with him my mother law & grandmother cancelled the gift deed given to him & it was registered. Then he sent a caveat to them & sub-register to stop it. We didn't respond to it & then he went to high court in Hyderabad. Now the case is in HC. Then he filed additional cases on my mother in law regarding the amount she took as she signed in some stamp papers & blank cheque also. She also took a loan on the building to repay his debts in which she & her elder daughters are the only legal heirs as the remaining 3 daughters registered back to their mother as she told she’ll get loan she gets a major stare in the building. Now she is in trouble as she signed in some stamp papers to that fellow. So kindly help us how can get the property back? Gift deed cancellation can we won in High court? At the time of registration my wife was a minor but registered as a major by writing a false age. In what way we can fight with him to save this family?