" 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. "
To pin Trump Sr or Trump Jr for treason there will need to be a prima facie case that for personal gain or possibly fear of blackmail a Trump furthered (or attempted to further) the interest of Russia in Ukraine or Syria. Nothing else counts IMHO because there needs to be a war.
It is a certainty that in the Syria war, Trump betrayed a militia that was created by the US. He did so against the advice of everyone who is anyone. Did he do this for personal gain or because Putin holds something over him?
