With several heirs all must dispose jointly.
If the property belongs jointly to several heirs, they can only sell by agreement. All co-heirs must consent to the sale and sign the contract or appoint a representative. If the consent of one co-heir is missing, title cannot be effectively transferred.
Before signing, have it checked whether all entitled persons are covered and whether the proceedings are already concluded. How shares of several owners take effect is explored in the post on buying an undivided co-ownership share.