Responses
They are blood related, or at least Haru and Tatsuya father is the same man (the one in the hospital).
The part before the last extra Tatsuya states clearly that he is going to deprive Haru of a father because he does not want him to know that they are blood related and are in an incest relationship.
One of the commentators bellow explain things better, but this is the gist of it.
They are half brother same of father but different mother
What result the document was reading by tatsuya? They are real silbing or not ? Who is real father of haru was tatsuya father or kaname father pls explant it