Don Jr, Eric and Ivanka are not natural born citizens. As Ivana was not naturalized before their births.
I just checked, and confirmed that. Ivana was not naturalized until 1988, after the three children were born. We don't know if Barron is eligible until we know when Melania was naturalized.
Who's eligible? Tiffany.
They weren't born in the US? Donald wasn't a citizen??