Wang Wei observed the young Battle Maniac Emperor for a while and could guess that it was a clone left by the real Battle Maniac Emperor in the tower to teach future disciples of the sect. While observing, Wang Wei recalled the information he learned about him through the history classes he had to take.
In fact, Wang Wei admires the Battle Maniac Emperor quite a bit. Among the three ancestors of the sect, he admired him most because of his determination.
According to what he knew, all the other sworn brothers and sworn sister of his ancestor Wang Qishan--also known as Emperor Qiyuan--also became Great Emperors.
After Wang Wei's ancestor became Emperor, he washed away the karma from his other two sworn siblings, giving them the chance to fight for Heaven Mandate in the following generation.