Do all family members have to sign the letter of understanding?

Legal analysis: the letter of understanding does not have to be signed by all family members. According to the relevant national laws and regulations, the letter of understanding must be signed by the parties themselves or their entrusted agents. You don't need everyone else to sign. The purpose of issuing letters of understanding is to reduce the punishment of criminal suspects, and some can release criminal suspects on bail pending trial.

Legal basis: Criminal Procedure Law of People's Republic of China (PRC).

Article 288 In the following cases of public prosecution, the criminal suspect or defendant sincerely repents and obtains the victim's understanding through compensation for losses or apology. (1) If a civil dispute is caused, it is suspected of a criminal case stipulated in Chapters IV and V of the Specific Provisions of the Criminal Law and can be sentenced to fixed-term imprisonment of not more than three years; (two) criminal cases of negligence other than dereliction of duty that may be sentenced to fixed-term imprisonment of not more than seven years. If a criminal suspect or defendant intentionally commits a crime within five years, the procedures specified in this chapter shall not apply.

Article 289 If both parties reach a settlement, the public security organ, the people's procuratorate and the people's court shall listen to the opinions of the parties and other relevant personnel, examine the voluntariness and legality of the settlement, and preside over the making of a settlement agreement.

Article 290 The public security organ may make suggestions to the people's procuratorate for leniency in cases where a settlement agreement is reached. The people's procuratorate may put forward suggestions for lenient punishment to the people's court; If the circumstances of the crime are minor and there is no need to be sentenced to punishment, a decision not to prosecute may be made. The people's court may punish the defendant lightly according to law.