258HMOs: persons not forming a single household
(1)This section sets out when persons are to be regarded as not forming a single household for the purposes of section 254.
(2)Persons are to be regarded as not forming a single household unless—
(a)they are all members of the same family, or
(b)their circumstances are circumstances of a description specified for the purposes of this section in regulations made by the appropriate national authority.
(3)For the purposes of subsection (2)(a) a person is a member of the same family as another person if—
(a)those persons are married to each other or live together as husband and wife (or in an equivalent relationship in the case of persons of the same sex);
(b)one of them is a relative of the other; or
(c)one of them is, or is a relative of, one member of a couple and the other is a relative of the other member of the couple.
(4)For those purposes—
(a)a “couple” means two persons who are married to each other or otherwise fall within subsection (3)(a);
(b)“relative” means parent, grandparent, child, grandchild, brother, sister, uncle, aunt, nephew, niece or cousin;
(c)a relationship of the half-blood shall be treated as a relationship of the whole blood; and
(d)the stepchild of a person shall be treated as his child.
(5)Regulations under subsection (2)(b) may, in particular, secure that a group of persons are to be regarded as forming a single household only where (as the regulations may require) each member of the group has a prescribed relationship, or at least one of a number of prescribed relationships, to any one or more of the others.
(6)In subsection (5) “prescribed relationship” means any relationship of a description specified in the regulations.