His great grandfather, Hamilton Fish II, was the Speaker of the New York State Assembly and a member of the United States House of Representatives, also a Republican.
His grandfather, Hamilton Fish III, served in the United States House of Representatives from 1920 to 1945 and he too was a Republican.
His father, Hamilton Fish IV, was a Congressman from New York, and a Republican
He, Hamilton Fish V or Jr., ran unsuccessfully for Congress in 1988 & 1994, as a Democrat.
Most scions of prominent lines start going off the rails by III, highly likely to be homosexual by IV and the very few V’s who manage to sneak through that gauntlet of instability and disinterested parenting all wrapped up in deviance are as nutty as a fruitcake. The old “shirtsleeves to shirtsleeves in three generations” became a truism for a reason.
He also served as a captain in the "Harlem Hellfighters" in WWI.
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There were two Hamilton Fish IIs (just to make things confusing), an uncle and a nephew.
The nephew fought with TR's Roughriders and was killed at San Juan Hill.
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After leaving The Nation magazine in 1987, [Hamilton] Fish [V] entered a three-way race for the Democratic nomination for the United States Congress in a Westchester County district held by Republican Representative Joseph DioGuardi. The national media took note of the race when his 100-year-old grandfather, Hamilton Fish III, described his grandson as a communist and contributed $100 to the Republican in the race. Wikipedia