There was sufficient evidence to support a petition pursuant to section 300, subd. (a) where parents had history of domestic violence in child’s presence. Father and mother engaged in substantial domestic violence in the minor’s presence. A 300, subdivision (a) petition was sustained. Father contended that the jurisdictional finding under section 300, subd. (a) was unsupported by substantial evidence. He contended that a petition could be sustained under subd. (b) (neglect), but that neither he nor mother abused the minor or harmed him, and he was not at risk of substantial harm. The appellate court disagreed and affirmed. Application of section 300, subd. (a) is appropriate when, through exposure to a parent’s domestic violence, a child is at risk of suffering physical harm. It clearly applied here, where father had an extensive history of physical violence, and had been consistently violent with mother throughout their relationship, including in the car while driving. Mother had also been attacked while holding the minor, putting him at risk of physical harm. The court also did not abuse its discretion by finding that the maternal grandmother was a de facto parent of the minor. She had assumed his day-to-day care for long periods and was protective of him.