The following individuals living with others or groups of individuals living together must be considered as customarily purchasing food and preparing meals together, even if they do not do so:

(a) a spouse of a member of the household;

(b) a child(ren) under 18 years of age, other than a foster child(ren), under the parental control of an adult household member who is not the child(ren)'s parent or stepparent;