Claim of legal heir on a sold property

Hi, We would like to finalize a small apartment for our Own use. We checked the parent document & infer that it was sold from the original land owner's relative thru a gift Will dated 1975.The will is Handwritten, signed by the original owner with 2 witnesses.Current value of the property is about 1.5 Cr and builder has obtained permission for 10 apartments in 2 storeys.We saw that the land owner's son has submitted legal heirship in 2005. However, there is no inference of his involvement during the initial sale of land in 1990 nor his NOC is enclosed.Property is already sold 3 times.We are the fourth buyer. Will there be any legal issues henceforth.