Family Quotes in City of Ashes

Clary acts like she has to help Jace because he's the brother she never knew she had, but the truth of the matter is she's more interested in him as a boyfriend than a brother. However, she emphasizes the fact that Jace is her brother to Simon, so that it won't hurt his feelings. (It doesn't work.)

As we learn later, Luke is wrong, at least as it applies to Valentine. He turns his affection for Jace off, and is capable of sacrificing or killing his own son if it means he gains power from it.

This is a repeated idea throughout the book, emphasized by the fact that Valentine, Jace and Clary's birth father, is such a despicable evil man.