Property Law

My dad and my uncle are joint holders of the house and they mutually decided to sell the 2nd floor. After the sale the terrace rights still belonged to my dad and uncle and the guy who bought the 2nd floor is only the owner of his floor. Few months back my dad and uncle sold the 3rd floor or terrace (as there was only one room on the terrace) to another person and the terrace rights above that was also sold to the person who bought the 3rd floor. Now before getting the construction plan passed by the municipality for the 3rd floor the new owner had to get the NOC from all the owners on the premises. At this time the guy who has previously bought our 2nd floor started demanding for money to sign the NOC. I need help to understand the following: 1. Can the owner of the 2nd floor really demand money from my family. ( he doesnot have any written understanding that my family will check with him about further selling of any part of our property as he is not a part of our family and he is only the owner of one single floor). 2. If we sign the NOC for the new owner can this person create any trouble?