Legal heirs claiming joint property after 18 years

Sir , We are living in a BDA/BBMP ( Bangalore Development Authority) approved layout past 8-10 years. Now we see that few legal heirs have care claiming share based on joint family partition that happened 18 years ago ( in 1991). Here is the history. There were two brothers X & Y. They had property which was in joint possession - 3.3 acres of land ( got from father who in turn got via inam abolision act). X & Y sold portion of it measuring 1.92 acres together while in joint family . Remaining 1.38 acres of land was in joint possession. In 1991 , Mr . Y after death of X , got this 1.38 acres of land in his name via mutual partition with X's wife ( X's wife was given some other piece of land which they jointly owned). There are records to indicate this. X's sons were major that time. They were not involved in this partition and done between Y and X's wife only. Later Mr .Y sold this 1.38 acres of builder and sites were created there in 2004. People started living there peacefully , constructed homes. Now Mr.X son's have come up ,saying Mr .Y got possession of 1.38 acres illegally. They filed case in session court in 2009 , for entry of their names in MR . They got it done somehow . When residents appealed in high court , high court court ruled it in their favor asking X'sons to prove their ownership before entry in MR . Now in 2016 they have filed civil suit against X sons and person to whom Mr Y sold land including people who are living the layout. They are demanding half share in 1.38 acres. Question : Is this valid ? They have come almost after 18 years ? . How do you see chance of Mr.X's legal heirs now ? What about people living in layout with homes constructed paying taxes ? Do you see this case dragging for long ? What's the usual conclusions in such cases ? Regards H