20.—(1) Subject to the following provisions of this regulation a person shall be treated as responsible for a child or young person who is normally living with him and this includes a child or young person to whom paragraph (3) of regulation 19 applies.
(2) Where a child or young person spends equal amounts of time in different households, or where there is a question as to which household he is living in, the child or young person shall be treated for the purposes of paragraph (1) as normally living with—
(a)the person who is receiving child benefit in respect of him; or
(b)if there is no such person—
(i)where only one claim for child benefit has been made in respect of him, the person who made that claim, or
(ii)in any other case the person who has the primary responsibility for him.
(3) For the purposes of these Regulations a child or young person shall be the responsibility of only one person in any benefit week and any person other than the one treated as responsible for the child or young person under this regulation shall be treated as not so responsible.