(a) The duty to support a child under the age of 18 years, whether born in or out of wedlock, rests primarily upon the child's parents.
(b) Where the parents are unable to provide a minor child's minimum needs, a stepparent or a person who cohabits in the relationship of husband and wife with the parent of a minor child shall be under a duty to provide those needs. Such duty shall exist only while the child makes residence with such stepparent or person and the marriage or cohabitation continues.
(c) The duty to support a child under 18 years of age, whether born in or out of wedlock, shall rest equally upon both parents.
(d) Both parents have a duty to support their child over 18 years of age if such child is a student in high school and is likely to graduate. This duty ends when the child receives a high school diploma or attains age 19, whichever event first occurs.