Well, one moral might be the importance of family bonds. The old man and his grandson's relationship in the story highlights how family members should support each other through difficult times. It shows that love within a family can overcome various challenges.
The story's moral could also be related to the cycle of life. The old man represents the past and the wisdom that comes with age, while the grandson is the future. Their relationship shows how the past and future are connected and how we can learn from each other across generations.
Fan Xian was thought to be his grandson by old man Xiao because of Chen Pingping's misdirection. Chen Pingping deliberately made old man Xiao believe that Fan Xian was his grandson so that he could learn the secrets of the Divine Hall and other secrets from him. Fan Xian listened to Chen Pingping's plan and made old man Xiao mistakenly think that he was his grandson. In the end, before he died, old man Xiao revealed the secret of the Divine Hall to Fan Xian. After Fan Xian learned of his birth and secret, he did not expose the lie and gave old man Xiao one last comfort. Fan Xian was actually the adopted son of the Qing Minister of Revenue, Fan Jian, the Qing Emperor's son, Fei Jie's disciple, the Commissioner of the Qing Inspection Council, and the Law Officer of Taichang Temple. Old man Xiao finally realized that he had recognized the wrong grandson. Fan Xian was not his blood.
Another theme is the exploration of magic. Fanfictions often expand on the magic system in the original story. For example, they might introduce new spells or different ways of using magic that the grandson discovers. There could also be themes related to family and legacy, as the grandson has to live up to the reputation of the wise man. It's about how he honors his grandfather's teachings while also forging his own path in the world of magic.
I'm pretty sure Sizilien doesn't die in the Wise Man's Grandson manga. Usually, major character deaths are significant plot points and I haven't come across this one in this manga.
The compilation of family trees usually did not include grandchildren in the family tree. According to tradition, a family tree was linked to the family name, and only the descendants of direct blood relatives would be recorded. Grandsons were members of families with different surnames. Although there was no difference in blood relations between grandchildren, they were considered to have different identities in the compilation of family trees. However, modern society was gradually open and compatible with the way genealogy was written. Some families would include their daughters, sons-in-law, grandchildren, and granddaughters in the genealogy to adapt to the development of the times and the changes in family structure. Therefore, it was up to the individual and the family to decide whether or not to write their grandson into the family tree. There were no fixed rules.
The status of the eldest grandson and the eldest grandson was different. The imperial grandson referred to the son of the emperor's eldest son, while the imperial grandson referred to the title of the son of the emperor's eldest son after he was appointed as the crown prince. In terms of identity and status, the imperial grandson's status was higher than the imperial grandson's. The imperial grandson was the heir to the throne and had a position similar to the Eastern Palace. He was also given the title of heir to the throne. The eldest grandson of the emperor was the grandson of the emperor. He was a relative of the emperor and had a noble status, but he did not represent power. Therefore, the status of the imperial grandson was even more important and special.