History of Liao
Yelü Deguang was born in 902, before the founding of the Khitan empire (which would later become known as Liao dynasty). His father was the Yelü clan chieftain Yelü Abaoji, and his mother was Yelü Abaoji's wife Shulü Ping; he was their second son. As a young adult, he was described by the "History of Liao" as serious in his appearance and kind in his disposition, and often participating in his parents' governance of the state.