Claim ancestral property written in father's name when he was a minor

As per a partition document in 1950, my father's grand mother divided her land among her children and grand children some of whom were minor. A plot measuring about 6 cents was written in my father's mother's name and father's name who is mentioned as baby of 6 months old. My father passed away in 2009. His 7 siblings registered the whole 6 cents in his youngest siblings name without our knowledge in 2014.This sibling has constructed a house and is staying there with family in 3 cents. Don't my mother, me and my brother have a right to half the land? Also there is another property partitioned in 1957 wherein 6 cents is given in my father's mothers name , father's name and 3 of his siblings out of which 3rd sibling is mentioned as baby of 2 months old. This property is unoccupied.Pls let me know what steps to take in both cases.