Teresa Lisbon's mother was killed by a drunk driver when she was 12. The storyline (Red Tide) implied that Teresa then had to take over her mother’s role and care for her family of 3 younger brothers. After her mother’s death, her father became an abusive drunk and ended up killing himself (we don’t know whether he did this accidentally or on purpose, but Teresa said “...damn near killed me and my brothers too...”, so it may have been something like another drunken car accident, or simply neglect).