My father has 2 wife's , 1st wife 2 childrens and 2 nd wife 1 son, both are own sisters, lived toge

My father has 2 wife's , 1st wife 2 childrens and 2 nd wife 1 son, both are own sisters, lived together in my 2nd wife property, all 3 expired without doing any will. We all lived together, now 2nd wife son claiming that property in his mother name, he want to register in his name,but I am 1st wife son, I want property share as it is family property all my family members have contributed for the property, now 2nd wife son is created false family tree vomiting 1st wife's and there children's details and trying to get property registered in his name. As we are all lived together , and contributed to run the family lively hood, now he is cheating to give share fir 1st wife children's, now 1st wife son is in position, 2nd wife son is staying outside in his own property. My father registered property in 2nd wife's name because all the 3 members ( 1st wife, husband znd 2nd wife) were govt employees. And 2nd wife was getting less salary then the loan amount. Kindly help