family. Family lawyers are involved in … Because family law is the practice of law that relates to relationships and children, it can be one of the most emotional areas of law. 2) all blood relations. Laws on these topics vary from state to state. Family Law is part of the law that deals with relations within the family and issues related thereto. Most states define marriage as a civil contract between a man and a woman to become husband and wife. Most people chose this as the best definition of family-law: Collectively, those laws... See the dictionary meaning, pronunciation, and sentence examples. noun. Family Law Law and Legal Definition. The branch of law that deals with matters relating to the family, such as divorce and child custody. Family law encompasses marriage, adoption, divorce, custody, death, and estate planning. Family law addresses adoption, contested custody of children and the child support obligations that result. Definition of family law in English: family law. n. 1) husband, wife and children. 3) all who live in the same household including servants and relatives, with some person or persons directing this economic and social unit.