Law of decent & distribution related query.

I am summarizing a family case, seeking opinion from knowledgeable person/legal professionals/experts, with possible case reference and guidance.

1)      An age-old relative of mine passed away, leaving no spouse and children behind him.

2)      His blood related living relations are (i) his deceased eldest brother’s two sons and one married daughter and their children and (ii) his living elder brother having one married daughter.

3)      The deceased stayed as a family member of deceased elder brother’s family for more than 50 years, at Dum Dum, Kolkata after his transfer and till retirement and thereafter. He lived happily with the deceased elder brother’s family and even not shifted to an adjacent flat in a builder apartment which he bought.

4)      About two years back from the demise of this relative, the second elder brother who is staying in Salt Lake, Kolkata could convince my relative to stay away from deceased eldest brother’s family and take occupancy in his adjacent flat, thereby detaching from the comfort of his deceased eldest brother’s family. Three month’s thereafter, he took away the relative to his Salt Lake residence.

5)      The relative in question was not happy, though he could not disregard his living elder brother of this decision. Thereafter, he felt ill and suffered continuously and finally died a few days ago at his Salt Lake brother’s home.

6)      The relative expressed his unhappiness and discomfort in staying with his brother’s family at Salt Lake, to the frequent visitors of the deceased elder brother’s family members (Deceased elder brother’s two sons, their wives and their children), with a request to take him back to the family at Dum Dum. As per the family culture of non insubordination to the elders, the visiting relatives of the deceased elder brother’s could not force their Salt Lake uncle to accede to their request of taking back their younger uncle back, though they put their request.

7)      Just six month’s back, the Salt Lake uncle came to Dum Dum residence of the deceased elder brother and took away all the locked trunks and suitcases, including the one where he kept all his wealth holdings and documents. He also demanded the second key of his flat after collecting some items like TV, Kitchen appliances,  Geyser from the adjacent flat too.

8)      The son’s and other member’s of his eldest broth’s family could not disregard and allowed everything to take away by the second brother.

9)      On the death of the relative (youngest among the three brothers) the Salt Lake brother and the two sons of the relative went for cremation. There the Salt Lake elder brother objected to “MUKHAGNI” by anyone other than himself.

10)  Now that the relative’s wealth holding is voluminous, which consists of his superannuation, Sale proceeds of his Delhi owned house and the flat owned by him at Dum Dum? Exact volume can be determined by only his Salt Lake brother who is in possession of his document.

From the above summary of details, I seek guidance and legal implications in relation to the “ LAW OF DECENT AND DISTRIBUTION’. In case an uninformed “WILL or TESTAMENT” if executed without other’s knowledge and if nomination registered in the name of others apart from his Salt Lake brother.

What steps to be initiated by the deceased elder brother’s family, who do not have any details on his securities or others, to protect their interest, if at all any is there in their favour?

Any further clarification, if sought is welcome to provide judicious and helpful advice/guidance.