For the purposes of sections 110, 152, 158 and 171 and without prejudice to any obligations imposed by law or otherwise, the following provisions shall have effect, that is to say -
(a) a man shall be liable to maintain -
(i) his wife, and
(ii) any child of his, being a child who is under the age of 18 years or (save for the purposes of section 171) who is of or over that age and under the age of 21 years, and is receiving full-time education or instruction by day at any university, college, school or other educational establishment,
and
(b) a woman shall be liable to maintain -
(i) her husband, and
(ii) any child of hers, being a child who is under the age of 18 years or (save for the purposes of section 171) who is of or over that age and under the age of 21 years, and is receiving full-time education or instruction by day at any university, college, school or other educational establishment.