Complex sentence: Still a minor, John I was the last duke of Lower Bavaria for one year only; after his early death in 1340 the duchy of Lower Bavaria passed to Louis IV, who then reunited the duchy of Bavaria in January 1341.
Split into simpler sentences: Still a minor, John I was the last duke of Lower Bavaria for one year only. After his early death in 1340 the duchy of Lower Bavaria passed to Louis IV, who then reunited the duchy of Bavaria in January 1341.