Okay I've got a riddle idea.

A father and son are part of a heteronormative nuclear family unit, perhaps we don't state this outright but we only imply. Something happens that renders the father presumably irrelevant for the rest of this riddle. The son requires services that, according to mid 20th century American gender norms, would be performed by his father but not his mother. Yet the services are also of a nature that it would be difficult or unethical to perform them for a close relative.