“(1) In this Part, unless the context otherwise requires, de facto partner and de facto relationship have the same meaning as in section 2 of the Property (Relationships) Act 1976.
“(2) In this Part, unless the context otherwise requires, child of the de facto relationship,—
“(b) includes, in relation to any proceedings under this Part, a child (whether or not a child of either de facto partner) who was a member of the family of the de facto partners at the time when they ceased to live together or at the time immediately before the institution of the proceedings, whichever occurred first.