250(1)
A person is a member of another's family for the purposes of this Act if—
(a) he or she is the spouse or civil partner of that person,
(b) he or she and that person live together as if they were spouses or civil partners, or
(c) he or she is that person's parent, grandparent, child, grandchild, brother, sister, uncle, aunt, nephew or niece.
250(2)
For the purposes of subsection (1)(c)—
(a) a relationship by marriage or civil partnership is to be treated as a relationship by blood,
(b) a relationship between persons who have only one parent in common is to be treated as a relationship between persons who have both parents in common, and
(c) except for the purposes of paragraph (b), the stepchild of a person is to be treated as his or her child.