What happens when a son-in-law doesn't support his parents-in-law?

Legally, it's nothing. Because according to the law, the son-in-law has no obligation to support her parents-in-law.

Supporting the elderly is a traditional virtue and an obligation of children. Article 1067 of the Civil Code stipulates in detail the situation of children supporting the elderly, and the Law on the Protection of the Rights and Interests of the Elderly also mentions that the spouse of the supporter should assist the supporter in fulfilling his maintenance obligations.

Judging from these two relevant laws and regulations, the son-in-law is not explicitly required to support the woman's parents, and the legal scope of supporting the elderly is limited to: children born in wedlock, children born out of wedlock, adopted children, stepchildren and grandchildren who have the ability to support.

The son-in-law is not the legal supporter. In this case, the son-in-law can choose not to support Chen Laohan, but the law also encourages the widowed party to support the other parent.

Article 129 of the Civil Law stipulates that a widowed daughter-in-law who has done her main duty to support her in-laws and a widowed son-in-law who has done her main duty to support her in-laws are the first heirs.

Legally speaking, the son-in-law can't set the obligation to support the woman's parents, because the parents-in-law are imaginary blood relatives, which are determined by the wife's identity, and their obligation to support should be exercised by the wife, but in real life, it is generally manifested as the obligation of husband and wife to support each other.

After the wife died, the fictional relationship died, so there was no obligation to support. However, according to the traditional moral requirements, the widowed son-in-law should also fulfill the obligation to support the original in-laws, but this is only a moral requirement, not a legal requirement.