Clary's sister

Seraphina is the daughter of luke and Joselyn. She's half shadowhunter, half-werewolf. Her mum trained her to be a shadowhunter but she would rather be a downwolder, like her friend Maia and her dad, and of course, her not so boyfriend, boyfriend Raphael who happens to be the second in command of the New York clan.

You see Seraphina can't wait for Clary's 18th birthday, that's when her mum finally decides to tell clary everything about shadowhunters and downworlders and Seraphina won't have to tell any more lies. Clary already hates her enough for hiding a secret that tore them apart. and now Clary knows, with all the dangers that come with being apart of this world.

I'll probably come up with a better plot summary then that but this will do for now.