Lease deed registered on the basis of unregistered memorandum of understanding.

3 properties all purchased and registered jointly in the name six brothers. each hold 1/6 th share on all properties. After 10 yrs misunderstanding arose between brothers and finally an MOU was written that brothers 1&2 was allotted 1st property ,3&4 was allotted second property 5&6 was alloted 3rd property and can do business of their own.Further properties allotted to all have to be partitioned by way of family arrangements and same to be registered with the Registration Dept. A clause mentioned in the Mou is that this Mou will come to effect only after Registration and fulfillment of condition specified there in. Till date there was no partition and registration.Brothers 1 & 2 closed their business also enemity brewed between them .At this juncture 1st brother alone entered into lease deed (registered )for 15 yrs with 3rd party on the basis of Mou which was not registered and activated .1st brother forged the Mou that he is alone sole owner and possession of the 1st property.Now how to cancel that lease deed.