Must an inheritance, consisting of money from the sale of land, be disposed of when it is suspected that the land was usurped, while the rightful owners cannot be identified?

Your father's lawful wealth that he left behind is for you to divide according to your prescribed shares, even if there are rumors about its source, as long as they are not proven. It is stated in Al-Majmou' by Al-Nawawi: "Whoever inherits wealth and does not know how their inheritor earned it, whether from lawful or unlawful means, and it bears no distinguishing mark, then it is lawful by the consensus of scholars."