City of Bones
How we cite our quotes:
Simon pushed [her messenger bag strap] back up absently, his finger lingering at the bare skin of her shoulder. (2.139)
Clary sure doesn't recognize this lingering touch, and we're not sure if Simon's doing it consciously either, at this point. We're talking ten years of unrequited love here.
[Simon's] face was so familiar [Clary] could have traced its lines in her sleep. (2.161)
This is sweet, but it's more like brother/sister love than the romantic love Simon desires. If only he was her real brother, like Jace, (spoiler alert!) then maybe she would have romantic feelings toward him…
"Declarations of love amuse me, especially when unrequited." (3.57)
Jace's amusement at unrequited love is ironic because he has his own unrequited love for Clary, his sister. He'll get down off his cynical high horse soon enough.