Character last names?

My characters: Cain Jonas Jade (name might change) Skylar (Sky) Greyson (Grey) Jessica/ Ali/ Elle/ Maya (not sure on name yet) For last names all i have is.. Jonas Thorne Skylar Evans ( Sky Evans ) ALL i got, help? PLEASE answer my other question, easy ten pints! its urgent. http://uk.answers.yahoo.com/question/index;_ylt=AiZH439sgcdXDC8WSabQvGEHJ3RG;_ylv=3?qid=20121026154517AApGmRv