Mutation of land & NOC

I am from Siliguri, West Bengal. Siliguri falls under two districts. Half under Darjeeling, another half under Jalpaiguri. My home falls under Jalpaiguri district.Back story:My maternal gandma bought 7200sqft land from Mr. P T Lama in 1961. Later she sold 1800sqft to Mr. Subal Ghosh. After that she constructed a two storied building (both floor measuring 1296sqft) on the remaining 5400sqft land. She died intestate on 20/01/1997 leaving behind my maternal grandpa, my two maternal uncles (mama), my mom & my maternal aunt(mausi) & they jointly inherited the land & building each having 1/5th undivided share therein. Later on 14/9/2003 my grandpa died intestate leaving behind my two mama, my mom & my mausi, they jointly inherited the land & building each having 1/4th undivided share therein. During his lifetime my grandpa gifted his 1/5th share to my mausi. Thus my mausi became the 2/5th owner of the land & building (before my grandpa’s death). My mausi later sold half of her 2/5th share land (1080sqft) to Smt. Rinku Saha. My mausi died on 10/05/2005 intestate (she was unmarried) leaving behind my mom & two mama & they jointly inherited the remaining land & building (4320sqft) each having 1/3rd undivided share therein. My elder mama has two daughters & wife. My junior mama has one son & wife. I am the only child (son) of my parents. On 08/11/2007 through a deed of partition the 4320sqft land was divided among my mom & my two mama. My mom got 1485sqft land. My elder mama got first floor of the building measuring 1296sqft plus one garage in ground floor measuring 133sqft (this garage is inside the ground floor) plus a piece of land measuring 499sqft. My junior mama got total 1561sqft land including the ground floor of the building minus the garage. These figures are mentioned in the deed of partition. But these figures do not add up to 4320sqft. This error was not spotted during the making of deed of partition (in 2007). My mom died on 13/03/2013 intestate leaving behind my dad & me & we jointly inherit the land (1485sqft) each having ½ undivided share therein. We have not done mutation of our land(1485sqft). Relation between my two mama & us (my father & I) are very bitter. Now my junior mama’s son (my cousin brother) wants to do mutation of his share of land. Now he came to know about the above error & for this error he is unable to do mutation. His lawyer has advised him to submit NOC from my father & me along with a copy of death certificate of my mom. Now he is asking our NOC & a copy of my mom’s death certificate. Now my questions are: 1.If I want do mutation of my land (1485sqft) in future, will the above error cause any problem? If yes, then what to do? 2.As the relation between us & two mama are very bad, if we give my cousin brother NOC & my mom’s death certificate, can he do any cheating with us? Or does forgery of our deed to take over our land? 3.Are we (my dad & I) obliged to give NOC & my mom’s death certificate to my bro?