For the purposes of this subpart, a child is considered to be:

(a) A biological child who lives with the Federal employee;

(b) An adopted child;

(c) A stepchild;

(d) A foster child;

(e) A child for whom a judicial determination of support has been obtained; or

(f) A child to whose support the Federal employee, who is a parent or legal guardian, makes regular and substantial contributions.