It would be an unconstitutional attainder to prohibit the spouses, siblings, children, and first-degree nephews and nieces from running for any elective office after actual seating of an individual as a federal elected official; it would also be an extremely good idea, if we really care at all about limiting nepotism. Hell, I’d go so far as to include state and major local elections, too (Chicago mayors for $500… and the Daleys weren’t the first).
An anti-nepotism constitutional amendment would certainly upend South Florida politics, not to mention put spokes in the electoral plans of the Kennedy, Cheney, Bush, and Clinton families. Assuming this would be a good idea in principle, there are lots of details to consider. Should the ban be absolute, or just be limited to the offices the first person held? (I.e is there a meaningful difference between two Bushes or Clintons running for President and a Cheney running for Senate? ((Best joke of the day.))) Also, for some reason I feel more comfortable with the ban on children than the one on spouses and siblings. In particular, a spouses ban will harm women much more than men.
Although if we’re dreaming, big money in politics is a much bigger problem than nepotism, not that the two are unrelated.
Meanwhile, when will we resurrect the John Quincy Adams precedent and have a good former President serve in the House? Although with our luck we’d probably get the Andrew Johnson precedent and get a bad former President in the Senate.