US Constitution Series, Article III, Section 3

Article III. JUDICIAL DEPARTMENT

§ 3. Treason

Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court.

The Congress shall have Power to declare the Punishment of Treason, but no Attainder of Treason shall work Corruption of Blood, or Forfeiture except during the Life of the Person attainted.

It seems quaint to say this, but it would be unconstitutional to punish the children and grandchildren of someone convicted of treason;