Can wife transfer portion of husband's prop after his death (no will)

My grand father died in 1990 and have 3 son and 2 daughters and wife. Property partition did not happen legally and everyone stayed at their own portions since grand father's death. grand mother (died recently) did a registry 2 year back to one of his son's name about certain portion of the property without other son's or daughter's consent or even without informing them. is this legal or she had no right to transfer the portion.