Question: are clary and jace really siblings in shadowhunters?
Answer: At the end of City of Bones, Valentine Morgenstern, reveals to Clary and Jace that they are siblings, and his children. Jace is not Jonathan Christoper Wayland, as he believed, but Jonathan Christoper Morgenstern. ... Due to the fact that they are siblings and in love, it just makes them both pretty miserable.