Mezue ahịrịokwu na-esonụ: William bụ ọkpara Duke nke Brunswick Henry Onye Dị Nro site na alụmdi na nwunye mbụ ya na Sophia, nwa nwanyị nke Griffin Duke Wartislaw nke Anọ nke Pomerania. Mgbe nna ya nwụsịrị na 1416, ọ ketara Brunswick Principality nke Lüneburg nke ọ chịkọtara ya na nwanne ya nwoke nke ọkara bụ Henry Onye Udo. William ghọrọ onye ọchịchị dị ike; n'oge na-adịghị anya ọ banyere n'ọtụtụ esemokwu na ndị isi agbata obi dị ka Archbishop nke Bremen na Bishọp nke Hildesheim, ma kwado Count nke Schauenburg na Holstein n'ọgụ ha na Eze Eric nke Denmark. Ya na Margrave Frederick nke Meissen lụkwara ọgụ ma merie ndị
Ndị agha Hussite na 1421 Agha nke Brüx.