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