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In OTL the U.S. has had two Father/Son Presidents (Adams and Bush), your challenge is with a POD after George Washington takes office, have the U.S. have a Father/Son Presidential pair, but have the son serve as President first and then the father serve second. The terms can be at any point including up to the present day. The neither the father nor the son have to have served as President in OTL but bonus points if one of them did and even more bonus points if one of them did and they keep the same tenure in office.

Edit to add: This can also be a Mother/Son, Father/Daughter, Mother/Daughter challenge.
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