registered family settlement and unregistered will

In family members are A- father, B-mother, C-elder sister and D E F three brothers 1.an registered family settlement in the office of the registrar of stamp was done in 2000 and all family members A TO F had signed the document and major properties SAY 85% was distributed in A D E & F and the balance 15 % property after registered family settlement belonged to A and was of the sole ownership of A out of his own income and in an individual capacity. In 2014 a got expired and by way of writing will [unregisterd ] in 2013 he distributed his property in C and F. Now after the death of A mr E who got major share in registered family settlement does not agree with the registered family settlement of year 2000 and challenges the will by filling an FIR ISTGASA via court that mr A has never written will in his lifetime. the signatures of mr A on the registered family settlement in 2000 and on the will written in 2013 is same and genuine. my querry is that after registered family settlement on required stamp duty paid and duly registered with the registrar of stamps can mr E challenge the unregistered will by merely saying that the will is fake and file an FIR