Who is Ariel in maximum ride?

The relationship between Ari and Max is very complex. Book 1, and 2 you belive Ari to have a crush on max but at the same time wishing her dead. Then in book three (SPOILER ALERT) you find out Ari is Max's half brother so you may belive it to be that he loved her as a sister, and that he wished her dead because he felt she was Jeb's favorite kid. So there is no definite answer, as far as I know, but the answer, in my opinion, is something you must determine yourself.