Need help with 你们不是向着我的吗？ I found the phrase discussed in the title of this question on the 海贼王 manga (One Piece).  I have not found this phrase anywhere else, and have put this on other forums without much success.
Actually, it can be a real sentence in oral Chinese. 

向 can become a verb. It has 2 possible meanings based on the situation. 

First one mean "face to ..". The sentence can become "are you all facing to me?". 

The other meaning "are you on my side"/"don't you support me". 

For your case, I think it probably be the second meaning.