filial

The filial duty Ellesmere had paid to a father, who had no other claim to it than that he was his father, was now consoling to him [D'Alonville]; […]

If the admonition [to the parent] does not take effect, the son will be more reverential and more filial; […]

This, following Bateson, we may call the parental generation or P generation. Subsequent generations are called filial generations (abbreviated F) and their numerical order is indicated by a subscript, as first filial (F₁), second filial (F₂), etc.