Complex sentence: Albrecht, Duke of Saxe-Eisenach, (b. Altenburg, 27 July 1599-d. Eisenach, 20 December 1644) was the seventh, but fourth surviving, son of Johann, Duke of Saxe-Weimar, and Dorothea Maria of Anhalt.
Split into simpler sentences: Albrecht, Duke of Saxe-Eisenach, (b. Altenburg, 27 July 1599-d. Eisenach, 20 December 1644) was a ruler of the duchy of Saxe-Eisenach. He was the seventh (but fourth surviving) son of Johann, Duke of Saxe-Weimar, and Dorothea Maria of Anhalt.