Do you see what Cassandra Clare just did here? Jace is shitting on Luke and Clary’s bond as a family, which has some nasty implications that he is shitting on adopted families as well. As someone who has adopted five children, I can say fuck you.
I further want to explain something to both Jace and Cassandra Clare. Jace has known Clary for less than a month. Although Luke has been a distant neglective asshat about it, Luke has been more than a father to her than Valentine. And no, blood relations don’t trump adopted relations. It’s love that makes a family, not blood. Clary has every right to worry and feel concerned about Luke.
Also, just because Jace doesn’t have that connection to Luke (even though there are biological siblings) doesn’t lessen the value of Clary and Luke’s relationship. Let me say this again for people in the back: LOVE IS WHAT MAKES A FAMILY NOT BLOOD!