Article Three of the United States Constitution
The end of Section 3 specifically says that this punishment is not allowed.  When the Founders wrote "no Attainder of Treason shall work Corruption of Blood, or Forfeiture except during the Life of the Person attainted," they meant: "No heirs may be punished, and Congress can make the traitor forfeit (give up) their property, but only during their lifetime."  Their heirs would have to be able to inherit their property when the traitor died.