My family’s property was sold by my uncle and for years no one knew. Now that he’s deceased we find out, of course his children says nothing. We need

Im not sure that this question belongs in taxation plus i cannot really tell what you are asking.  If you think your uncle defrauded you somehow and it was along time ago, then probably what lawyers call the statute of limitations has passed.  In other words, it is too late to sue anyone.  Even so, it would be worthwhile to put all the facts together and seek out the advice of a lawyer.    What you wrote above does not really give me enough information to hazard an answer to you.