Basically I hate the fact that there's no future of us being together in the long run. I know that maybe others which are luckier, but that's not the case for us.
My soul is tangled in this relationship but at the same time we are adults and we have to realize that life should move on. I will probably marry a nice girl but it would not be the same, the passion and intensity will not be there.
We have something beautiful and most likely nothing will come out of it. Sometimes we both think about children (and a few times we were forced to think about it because of our carelessness..) but what future would they have..
The problem is the future, not the now.
He and his sister can have a future as a consanguinamorous couple. He should not let persecution, bullying, or prejudice, even from family, keep him from the person he loves. As he himself mentions, other people have managed.
Also, as he notes, the same passion and intensity would not be there with another person. It is unfair to marry someone under the pretense of monogamy when your heart belongs to another, regardless of who that person is. Consanguinamorous relationships should be legal, protected from bullying, and should have the fundamental right to marry. There are many reasons why. This situation is just one.