Right in grandmother's property which she got from her father

Dear Sir, I would like to buy a piece of land from a Hindu Nair family. Having read the document of the property, I have become confused. Please clarify my doubts so that I can either go ahead to buy it or abandon. The context to be examined by you is given below. A mother, who died without writing a will, gets her property by a partition taken place in the year 1956. This partition in 1956 took place based on the Maranapathram (Will) of her father. This diseased mother has three children who are alive now. Two males and 1 daughter. All of these three children are now senior citizens. The daughter of the diseased mother has five children who have born before 1976; a period when the Marumakkathayam existed and Joint Hindu Family System (Abolition) Act has not come into force. Based on the above given background, let me get into the major point. The three children, 2 males and 1 daughter, of the diseased mother entered into a partition and divided the property in an agreeable manner among them. This partition has been registered in the year 2013. I am trying to by the shares of the two males. My concern: The one daughter who entered into the partition along with her two brothers from whom I am trying to purchase the property, has 5 children who have born before 1976. 1) Don't the five children of the daughter of the diseased mother have right in the property of their grandmother as the five children were born before the Kerala Joint Hindu Family System (Abolition) Act that came into existence in the year 1976? 2) As far as these 5 children of the daughter of the diseased mother are concerned, isn't the property of their grandmother a Thawazhi property (hence a right ?) though the five children's grandmother got it by a partition taken place based on the will of her diseased father?