(a) The following are obliged to support each other—
(1) husband and wife;
(2) legitimate ascendants and descendants up to 18 years of age;
(3) parents and children and the legitimate descendants of the latter up to 18 years of age;
(4) the adopter and the person adopted; and
(5) parents and illegitimate children who have been recognized as children by written acknowledgment of the natural parent or by decree of a competent court.
(b) Brothers and sisters also owe to their brothers and sisters, even when only on the mother's or father's side, the aid necessary to maintain their existence, when through a physical or mental defect or for any other cause not the fault of the person requiring support, such person cannot provide for himself.
(c) With such support is included the expenses necessary for the elementary education and teaching of a profession or trade.