mutation vs legal heir certificate

Settlement ROR finalised and published in the name of A during 1981for one property. B & C the so called legal heirs of A sold the property to D during 2009. The property mutated in the name of D during 2010. Mutation was never done in the name of B & C. Now we want to purchase the property from D and asked them the legal heir certificate of A. To which D is replying that mutation was already done in his name and the revenue officials already saw the legal heir certificate of A and then only the property was mutated in favour of him(D) by following the procedures of mutation manual and as such legal heir certificate is not required. please suggest whether we can ignore the legal heir certificate as the property is mutated in the name of D.