Trần Quốc Tảng was born as Prince Hưng Nhượng (興讓王, Vietnamese: Hưng Nhượng vương) in Yên Sinh fief (now Đông Triều District, Quảng Ninh) as the third son of Trần Hưng Đạo, leader of Yên Sinh's line in Trần clan. After the 1237 event in which Trần Liễu, Trần Quốc Tuấn's father, was forced by grand chancellor Trần Thủ Độ, to give up his pregnant wife Thuận Thiên to his younger brother Trần Cảnh, an inherited hatred began to take form between the Yên Sinh's line of Trần Liễu including Trần Quốc Tuấn and Trần Cảnh's line including the emperors Thánh Tông and Nhân Tông. Before his death, Trần Liễu made his son Trần Hưng Đạo promise to revenge for him by taking over the throne but due to the situation of Đại Việt when the Trần Dynasty had to face with three consecutive invasions from the Yuan Dynasty, Trần Quốc Tuấn preferred keeping a harmony between him and Trần Quang Khải who was the other commander of Đại Việt's army and also a member of Trần Cảnh's line.