Otto Henry was the eldest son of the Duke
Otto II of Brunswick-Harburg (1528–1603) from his first marriage with Margaret (1530–1559), the daughter of the Count John Henry of Schwarzburg-Leutenberg. Otto Henry was educated under his father's strict supervision. He was taught science, but Otto II had strictly forbidden the instruction of fine arts. Otto Henry studied at the University of Strasbourg, and was a canon at
Bremen for a while, but then chose a military career. In 1590, he led the cavalry of the Duke
Alessandro Farnese in the
Eighty Years' War and showed great courage in the battle of
Ivry on 14 March 1590. He was seriously wounded in this battle. Otto Henry died a year later, in Brussels in 1591 at the age of 36. Since he died before his father, he never inherited Harburg. == Marriage and issue ==