Oral Partition

These excerpts are from the judgments mentioned with may be useful, just check-

#     “The family settlement (may be even oral) must be voluntary and should not be by fraud, coercion or undue influence. The family arrangement must be a bonafide one so as to resolve family disputes and rival claims by a fair and equitable division.

Kala v. Deputy Director of consolidation, AIR 1976 SC 807. Also Sahu Madho Das v. Mukund Ram, AIR 1955 SC 481.”

#   “The family arrangement may be even oral in which case no registration is necessary. The registration would be necessary only if the terms of the family arrangement are reduced into writing.  Even If the family arrangement is not registered, then it can be used as collateral purpose.” Ibid. Also see  Tek Bahadur Bhuji v. D. S. Bhuji, AIR 1966 SC 292.

oral familty settlement, partition of property   is perfectly valid

Oral partition of Ancestral land had done between my grandfather and his two other brothers at the time when they was alive, land is located in seven different location,
location no. 1,2,3 take my grandfather
location no. 4,5 brother no.1
location no. 6,7 brother no.2
each brothers occupied land is nearly equal, it had done around 65 years back,
location no.3 has been sold by my grandfather in 1972, after that each brothers heir enjoing that land and developed there locations
but all land is in jointly name of 18 person
in 2007 that all 18 has made a agreement on 100rs stamp paper 'our partion of land had done 62 years back and now nobody has objection on that partion' in presence of 3 witness,
now the heir of brother no.1 and 2 want to file a suit under hindu succesion act and want to do thee part of every location

i have invested lot of money in my location i have only xerox copy of that agreement.
is there claim is void?
is oral partion is invalid?
how can i protect and how are my chances to win?
please give me advise
thanks,