How we cite our quotes: (Part.Chapter.Paragraph)
Quote #7
"Family is more than blood. Valentine isn't my father. Luke is." (1.3.87)
See? The idea from the last quote has already been repeated a chapter later. Clary is much closer to Luke than she ever will be to Valentine. Being almost murdered by your father puts a crack in that relationship.
Quote #8
"You know how the bonds of family are, my lady," said Jace, recovering his voice. "They cling tightly as vines. And sometimes, like vines, they cling tightly enough to kill." (2.8.338)
We doubt Jace and Valentine would be arch nemeses if they weren't related. It's those family bonds that make their animosity stronger. Love and hate are two sides of the same coin.