Following Yeon Gaesomun's death around 666 Namsan joined forces with his elder brother Yeon Namgeon against their oldest brother Namsaeng, who ultimately fled to Tang China to seek its aid.
After the death of Yeon Gaesomun, Namsan joined forces with his older brother, Yeon Namgeon, to oppose their oldest brother, Namsaeng, who eventually sought refuge in Tang China for support.