 He was a grand-nephew of Tian Chou, an official who served under the warlord Cao Cao in the late Eastern Han dynasty.In 220, after Cao Pi (Cao Cao's son and successor) ended the Eastern Han dynasty and established the state of Cao Wei with himself as its first emperor, he wanted to honour Tian Chou for his good moral character.However, as both Tian Chou and his son were already deceased, Cao Pi decided to make Tian Xu the successor to Tian Chou, and he awarded Tian Xu the title of a Secondary Marquis (關內侯).