Step parents are entitled to apply for a child arrangements order as per section 10 - Childrens Act 1989 if any of these apply -
(a)any party to a marriage (whether or not subsisting) in relation to whom the child is a child of the family;
(aa)any civil partner in a civil partnership (whether or not subsisting) in relation to whom the child is a child of the family;
(b)any person with whom the child has lived for a period of at least three years;
(c)any person who—
(i)in any case where a child arrangements order in force with respect to the child regulates arrangements relating to with whom the child is to live or when the child is to live with any person, has the consent of each of the persons named in the order as a person with whom the child is to live;
(ii)in any case where the child is in the care of a local authority, has the consent of that authority; or
(iii)in any other case, has the consent of each of those (if any) who have parental responsibility for the child.
(d)any person who has parental responsibility for the child by virtue of provision made under section 12(2A).