Unrelated people of one gender may not generally have intimate physical contact with members of the opposite gender (negia). The prohibited types of contact are any that express affection or promote interpersonal relationships or intimacy.  Negia does not apply to:
For Males--mother, grandmothers, daughters, granddaughters, and other descendants and antecedents.
For Females--father, grandfathers, sons, grandsons, and other descendants and antecedents.