17. For the purposes of this Part a child shall be taken to be in need if—
(a)he is unlikely to achieve or maintain, or to have the opportunity of achieving or maintaining, a reasonable standard of health or development without the provision for him of services by an authority under this Part;
(b)his health or development is likely to be significantly impaired, or further impaired, without the provision for him of such services; or
(c)he is disabled,
and “family”, in relation to such a child, includes any person who has parental responsibility for the child and any other person with whom he has been living.