He succeeded to his father's lands because his older brother Michael Komnenos had been abducted and imprisoned in Constantinople. After succeeding his father in or shortly before 1289, Constantine ruled Thessaly and Central Greece from Neopatras. He was assisted by his younger brother Theodore Angelos, who died c. 1300. Early in his reign, Constantine's mother entered into negotiations with the Byzantine Empire and, in exchange for recognizing nominal Byzantine suzerainty, Constantine was invested with the court title of sebastokrat*r.
Theodore Angelos
Constantine