Since the early 1990s, the relationship between mother in law and daughter in law in rural China has undergone a significant change, expressed by the loss of mother in law’s authority and domination over daughter in law. This phenomenon indicates a reform of family resource distribution within the household, namely, the young generation gets upper hand in the labor market, and as a result, the daughter in law’s control over mother in law’s life resources, to a certain extent, threatens mother in law’s old age security. In a further analysis, it shows that the patriarchal kinship system places mother in law and daughter in law in contradictory positions for getting benefits: the son is the provider of his mother’s old age security; in the meanwhile, he is also the key investor of his own son who is the provider of his wife’s security. That means, the more resources provided to the mother, the less investment would be in the daughter in law. This result reflects that while gender equality is improved in many other aspects, it is still patriarchal in character to a certain extent.