We have a flat in the name of Father, Mother and a son. The father is deceased. The family has one married daughter and three sons (out of which one son is co-owner). We want to sell the flat and one of the buyer's bank is asking for an NOC from other children who are not the co-owners (2 sons and the daughter) for the deceased father's share. There is no dispute at all among any member. What is the format of the NOC and what is the procedure and on what type of stamp paper this would be required? Everyone is in different cities and one of the son is currently out of India. Please advise.