A son/daughter is defined as any child under 18, or over 18 if incapable of self-care, and who is a biological, adopted, or foster child, a stepchild or a legal ward, or a child for whom you are financially responsible and supervise on a day-to-day basis. The OFLA definition is the same, but also includes an adult child, over 18 and not substantially disabled, who needs care for a serious health condition.