Complex sentence: Chinese historical texts unequivocally state that the Xianbei were descendants of the Donghu, which used to be believed to represent the "Eastern Hu" based on the Chinese record.
Split into simpler sentences: Chinese historical texts unequivocally state that the Xianbei were descendants of the Donghu. The Xianbei were descendants of the Donghu, which used to be believed to represent the "Eastern Hu" based on the Chinese record.