Great-grandfather, great-grandfather, and great-grandfather were the Chinese names for family members. According to the information provided, his great-grandfather was the third generation, and his great-grandfather was the fourth generation. However, there was no clear explanation regarding the Mystic Ancestor in the information provided. Thus, it was impossible to determine the seniority of the Mystic Ancestor.
Well, here's a story. There was a beautiful princess. She was locked in a high tower by an evil witch. Her grandfather had left her a magic key before. She used the key to open the door of the tower. Then she started her journey to find the witch and break the spell. Along the way, she met a brave knight and they fought together against the witch.