It goes without saying that, given that one actor is black and one is white, the characters of Johnny and Sue Storm can't possibly be full brother and sister in this movie, as they are classically known as being. What their relationship is actually going to be is unclear. Will Sue be adopted (we're assuming Sue would be the adopted child in that scenario, given that we know Johnny's father is black in this movie)? Will they actually be a couple? Will they be related through marriage in some way (step brother and sister, for example)? Again, we'll have to wait and see exactly what their relationship is, but we know they have the same surname but couldn't possibly be full brother and sister like the classic comic book versions and the versions from the last movies.