Principality of Lüneburg
He was the second surviving son of Duke Ernest I of Brunswick-Lüneburg and assumed the rule in the Principality of Lüneburg upon the early death of his elder brother Francis Otto in 1559. He and his younger brother William fell out with each other in 1569, when Henry married the Ascanian princess Ursula of Saxe-Lauenburg (1545–1620), daughter of Duke Francis I, and demanded the partition of the Lüneburg lands.