Trần Ích Tắc was born in 1254 as the fifth son of the Emperor Trần Thái Tông, he was entitled Prince Chiêu Quốc in May 1268. Besides his elder brother the Emperor Trần Thánh Tông, Prince Chiêu Quốc had two other famous brothers who were grand chancellor Prince Chiêu Minh (Chiêu Minh vương) Trần Quang Khải and Prince Chiêu Văn (Chiêu Văn vương) Trần Nhật Duật, both Trần Quang Khải and Trần Nhật Duật were important generals of the Trần Dynasty during the second Mongol invasion of Đại Việt. Although Trần Quang Khải was a famous poet and Trần Nhật Duật was well known for his knowledge, the most famous prince of the Retired Emperor Thái Tông before the war was still Trần Ích Tắc. It was said that Prince Chiêu Quốc was not only intelligent but also fond of learning, besides a broad knowledge of history, art, literature, Trần Ích Tắc was even a skilled player of cuju and xiangqi. The palace of Prince Chiêu Quốc in Thăng Long was a renowned school of the capital where educated many scholars including some future prominent officials of the Trần Dynasty such as Mạc Đĩnh Chi or Bùi Phóng.