Why is the Monkey King surnamed Sun?

Because the Bodhi ancestor took a surname' Yan' from the Monkey King. Yan Zi went to a beast, but it was a Gu Yue. The ancients are old, and the moon is yin. Old Yin can't be educated, so teach him the surname' Yi'. The word Jue went to the side of the beast, but it was a child line. The son is male, and the baby is fine, which is in line with the theory of baby, so the surname is' Sun'.