John Doukas Vatatzes, born in about 1192 in Didymoteicho, was probably the son of the general Basil Vatatzes, who was killed in battle in 1194, and his wife, a cousin of the Emperors Isaac II Angelos and Alexios III Angelos. John Doukas Vatatzes had two older brothers. The eldest was Isaac Doukas Vatatzes (died 1261), who died young. Through his marriage to Eudokia Angelina he fathered Theodora Doukaina Vatatzaina, who later married Michael VIII Palaiologos. The middle brother's name is unknown, but his daughter married the "protovestiarios" Alexios Raoul.