If one doesn't know that some property belongs only to her(propety is only registerd at the name of her grandfather in law), but due to lack of knowledge divides her propety by signing on panchanama by herself and by her sons, giving half of the propety to her sons and other half to other party.(who happen to be the grandson of brother of her grandfather in law),
This has happend in 1984, now her sons came to know that property their only how can they claim it back.