Dennis was born in Burke on Feb. 26, 1955 to his parents Andrew W. and Eleanor R. (Herndon) Klein. He graduated from Burke High School in 1973. He had various jobs, but his primary occupation was truck driving.
In May of 1975 he was united in marriage to Vickie Stoltenburg. To this union a daughter, Katie, was born. This marriage later ended in divorce. Dennis then married Mardella Graf and to this union a son, Nicholas, was born.
Den was often described as having a heart of gold. His hobbies included fishing, coin collecting, volunteering at the Butterfly House in Sioux Falls and attending church activities.