The Noble Demigods are the children of the Noble Gods.
After the Admonition
After the Admonition and consequently the chaining of the mortal bodies of the gods, no Noble God other than Arthe could birth demigods. Over this period, that lasted centuries, most of the demigods died and Arthe gave birth to only one: Lianna, which is currently the oldest demigod still not Stonestruck.