"There are three kinds of unfilial, and unfilial is nothing" has always been regarded as the shackles of feudal thought, and then some people say that Confucianism destroys human nature, Mencius has no human feelings, and so on. Because they understand "there are three unfilial sons and no heirs" as "the greatest unfilial is to carry on the family line", this sentence has great magic in the feudal era with the theme of "loyalty and filial piety". In order to continue, both families and poor people will do their best. Followed by a series of special social phenomena such as adoption.