Question: is jace actually valentine's son?
Answer: Jace is not Jonathan Christoper Wayland, as he believed, but Jonathan Christoper Morgenstern. ... Instead, he is Jonathan Christoper Herondale, the son of Valentine's right-hand man Stephan Herondale and his wife Cecile. Valentine raised Jace because he had experimented with Jace's blood while Cecile was pregnant.