well...been in love with some one of a family is not a strange thing..it happens everywhere..its only that we grow and think maturely and then get to know whats wrong and whats right..most of those issues about who to be in a relationship with are covered in the bible, i give you (leviticus chapter 18 verses 1 to 23) you will surely find your answer in there and i hope it helps...to me it seems this step brother is of distant to you but he is your cousin, just think wisely and dont! the book i gave you read will cover all you want and i think you will be happy..with it..lol

 sorry for seeing this late...just came across it as i was also seeking help as am in love with my mothers sister..my aunt...but i have to follow the bible..there would be too much emotional break down,family breakups, and we would only be in a world of our own..the 2 of us..cant even have children ...its just digusting thinking of it..hope i helped though late,

  cheers!