Can family members ask each other for a letter of understanding?

Family members come forward on their own. If it is a criminal case, the defense lawyer you entrust is responsible for the criminal part, and the letter of understanding belongs to the civil negotiation part. If there is an agreement that lawyers can assist, it will be a little better for some criminal cases without lawyers, and the responsibilities that family members should bear will still be borne. What specific criminal cases need a letter of understanding? It is suggested that professional criminal defense lawyers should be entrusted to intervene as soon as possible, and effective defense work should be carried out in combination with specific cases and evidence, so as to strive for lighter punishment and mitigated punishment, and try to get bail pending trial and probation if certain conditions are met.