Simplify the following text for a Grade 11 native English-speaking person.
Original: Johann II , Duke of Saxe-Weimar ( or John II ) , died young but left eight surviving sons who ruled together , Three died , ( including Bernhard of Saxe-Weimar , the youngest , the famed general ) and a will ordering them to rule jointly .
Simplified: Johann II , Duke of Saxe-Weimar ( or John II ) , died young leaving eight surviving sons ( including Bernhard of Saxe-Weimar , the youngest , the famed general ) and a will ordering them to rule jointly .