Dennis dagba ni Kenesaw, Nebraska, ati Lincoln Nebraska, ti o jade lati Ile-iwe giga Lincoln High School ni odun 1955; okan ninu awon omo ti won jo wa ni kilaasi je akowe pelu apanilerin-in, Dick Cavett.. 
jẹ́ ààrẹ orílẹ̀-èdè Ekuaṣálẹ̀ tẹ́lẹ̀pọ̀àwọn ààrẹ ilé Ekuaṣálẹ̀.[ 