Louis was born on 7 May 1328 Rome when his parents travelled there for his father’s coronation as Holy Roman Emperor, hence his nickname “the Roman.”
When his father died in 1347, Louis succeeded him as Duke of Bavaria (as Louis VI) and Count of Holland and Hainaut together with his five brothers. Louis released Holland and Hainaut for his brothers William I and Albert Iin 1349.
since he expected to acquire the Polish crown by his marriage with Cunigunde of Poland, a daughter of Casimir IIIand Aldona Ona of Lithuania. Later claims against William and Albert were not successful. Hence Louis supported his mother during her war with William.
Margaret II, Countess of Hainault, and a member of the House of Wittelsbach. Louis was Duke of Bavaria as Louis VI (1347–1365) and Margrave of Brandenburg (1351–1365) as Louis II. As of 1356, he also served as Prince-elector of Brandenburg.
In December 1351 Louis VI received Brandenburg from his older half-brother Louis V of Bavaria in exchange for the sole rule of Upper Bavaria. Less experienced than Louis V, he was also challenged by the “False Waldemar”, an impostor who claimed Brandenburg and got support from several cities and Holy Roman Emperor Charles IV until the Wittelsbachs came to terms with Charles. Louis also had to abandon claims on fiefdoms in Mecklenburg and Pomerania. With the Golden Bull of 1356, Louis secured the electoral dignity. In 1358 Louis was absolved from the papal excommunication.
The early rulers came from several different dynasties, but from 1415 Brandenburg and its successor states were ruled by the House of Hohenzollern for over 500 years. From 1618 onward, Brandenburg was ruled in personal union with the Duchy of Prussia. The Hohenzollerns raised Prussia to a kingdom as the Kingdom of Prussia in 1701, and from then on Brandenburg was de facto treated as part of the kingdom even though it was legally still part of the Holy Roman Empire.