26In this Schedule, the following expressions have the following meanings respectively, that is to say—
" child " means a person who would be treated as a child for the purposes of the [1965 c. 53.] Family Allowances Act 1965 ;
" local authority " means a rating authority, a county council or the Greater London Council;
" relative " means any of the following, that is to say, son, daughter, father, mother, brother, sister, grandparent, grandchild, uncle, aunt, nephew and niece ; and, in deducing relationships for the purposes of this definition, an adopted person shall be treated as the child of the person or persons by whom he was adopted and not as the child of any other person and, subject as aforesaid, any relationship of the half-blood shall be treated as the relationship of the whole blood, and any illegitimate person shall be treated as the legitimate child of his mother.