Complex sentence: At the turn of the 13th/14th centuries he, together with the Turk El Temür, was a member of the group around Qaishan, a nephew of Temür Khan who was appointed to defend Mongolia against the Chagatai Khanate under Kaidu, the grandson of Ögedei.
Split into simpler sentences: At the turn of the 13th/14th centuries he, together with the Turk El Temür, was a member of the group around Qaishan. Qaishan was a nephew of Temür Khan and appointed to defend Mongolia against the Chagatai Khanate under Kaidu, the grandson of Ögedei.