Complex sentence: Though Leonardo's relationships with his other brothers Michelangelo and Donatello are not as volatile, both have made comments alluding to the high standards the former has set, and his tendency to make them look bad.
Split into simpler sentences: Though Leonardo's relationships with his other brothers (Donatello and Michelangelo) are not as violent. Both have made comments alluding to the high standards the former has set, and his tendency to make them look bad.