Can a son claim his share from the inherited property

Dear Sir/Madam, I have queries regarding purchasing inherited land which was sold by a family with a minor son. One Mr. Dhobhi Thimmaih was in possession of the 1 acre-11 guntas of land and sold it to Mr. Shyamanna in 1965, Two years later he purchased it back from Mr. Shyamanna through sale deed. Later on Mr. Dhobhi Thimmaih and his wife and also his only son Mr. Yellappa died. RTC is transferred in the name of daughter in law 'Lakshmamma' in the year 96-97. In Year 2009, 'Lakshmamma' and his only son Yallappa ( same name as father) along with his son Madhusudhan 19 years old and wife Chenamma representing minor son Sujay aged about 12 years sold 20 guntas ( half acres) of the land to one Kantharaju and another half to Manjunath, remaining to mr. Patalappa. Now I am planning to buy 3 gunts(3267sft) from Kantharaju. Does the minor son have the rights to claim share in this property? Can he challenge the sale of this property? He would have already crossed 21 years as on today. But sale is 9 years old. I consulted a advocate in the locality. Initially he said Minor son can challenge it as 12 years have not passed after sale. But after further discussion, he advised me to go ahead and purchase as there is no risk. kindly request you clarify on the below queries. 1) Does Mr. Sujay have the rights to claim share in this property now? He would have already crossed 21 years as on today. 2) if he has, Can the sale to Kantharaju become void or can Sujay only ask for partition to get his share? 3) What will be the share of Sujay incase he has the rights to claim now?. Since his father is alive, I guess it would be 50% to grandmother(Lakshamma), remianing 50% further divided into father, elder son and Sujay. 4) If I buy part ( 3 guntas) from Kantharaju, any chance this sale can become void, if Sujay demands his share ? Kantharaju is keeping remaining land for himself.