"William, Duke of Brunswick (German: Wilhelm August Ludwig Maximilian Friedrich; 25 April 1806 – 18 October 1884), was ruling duke of the Duchy of Brunswick from 1830 until his death.
William was the second son of Frederick William, Duke of Brunswick-Lüneburg, and after the death of his father in 1815, was under the guardianship of King George IV of the United Kingdom. He became a Prussian major in 1823. When his brother, Charles, was deposed as ruling duke by a rebellion in 1830, William took over the government provisionally. In 1831, a family law of the House of Guelph made William the ruling dukepermanently. William left most government business to his ministers, and he spent most of his time outside of his state at his possessions in Oels." - (en.wikipedia.org 01.01.2020)
