Building a Century-Old Family Since the Sui and Tang Dynasties

Wu Xin, whose soul traveled through a certain historical novel world, was notified by the bound system to build a family that would survive for five hundred years. One problem was that he did not have the memory of the original owner to fuse, so he could only move forward gropingly. He was a beggar who climbed up to Li Yuan and offered his advice to help him overthrow the Sui Dynasty and ascend to the throne, thus kicking off the Tang Dynasty. It wasn't until after the Xuanwu Sect incident that he felt that his mission was finally developing steadily, and he received a mysterious letter: "My lord, I have lost contact with you for more than ten years and finally found you. You are so powerful. You can become the new emperor's confidant on your own. When we come to hold the new emperor hostage together, our great cause can be completed in an instant." Wu Xin was dumbfounded now. Who is this original owner? Did the system send the wrong task?