If the victim can sign, is the letter of understanding signed by family members valid?

Whether it is the signature of the victim himself or the signature of other family members, it is ok and conforms to the actual situation. As long as the victim approves or agrees, or this is the case, it is true and effective.

The criminal letter of understanding itself has no fixed format. 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. Therefore, the letter of understanding is sent by the victim to the criminal's family, and is generally handled by the responsible lawyer for the criminal suspect.

The premise of the letter of understanding is that the victim has been injured, and it should be stated that the compensation has been reached and the actual compensation has ended. If the victim is not hurt, there is no need to express it. However, the focus of the letter of understanding should be to make it clear that the victim has understood that the victim requests to be exempted from investigating the criminal responsibility of the defendant (criminal suspect).