Brother Gift Deed the Ancestral Property which was in all siblings name earlier

My Elder brother took all of us (two younger brothers and a younger sister) in confidence in 2011 before my marriage saying we need a house to get your marriage in a good family. He asked us to transfer the ancestral property in his name so that he can take home loan and once home loan gets over subsequent brother can construct the first floor and second floor so on. So that all three of us should have equal rights, this all agreement was done orally since he was elder in the house as our parents were not there we agreed to his terms believing he will distribute when time comes. To construct the house I too spent around 7-8 lakhs by taking gold loan and with my savings regularly. I did crime sharing my ATM pin and he used that account to withdraw amount regularly. My younger brother expired in 2019 due to Type-1 diabetes. When I asked him that I will construct the first floor as discussed earlier. Now my elder brother initially mentioned documents are missing in LIC Housing Finance Limited gifted that property in his wife's name (my sister-in-law's name) without my knowledge and claims that he owns the property and doesn't give any share to me now. The property was purchased through my mother's ornaments and grandfather and father also contributed to it. Now he has all the documents of the property and not sharing anything and kept all the documents of property. How will I proceed legally to get my share from law. How can claim my ancestral property now.