Complex sentence: Yoshitsune was the ninth son of Minamoto no Yoshitomo and his older brother Minamoto no Yoritomo founded the Kamakura shogunate.
Split into simpler sentences: Yoshitsune was the ninth son of Minamoto no Yoshitomo. Yoshitsune's older brother Minamoto no Yoritomo (the third son of Yoshitomo) founded the Kamakura shogunate.