If Harry is the Scorn of an angel, then maybe his father is Mac. Mac and Malcolm have similar letters, and Mac is in every book(?). It would make sense why Mac now a somewhat mortal man. He sacrificed his angelicness for the sake of the future, but he still looks after his son as much as he can. In Cold Days after the Outsider attack, Mac can't help Harry because, as Mac said, "He's out," but what have we seen in the past with angles, balancing the scales. If Mac would have told Harry too much information, then the scales would not have been in balance. But he was able to help Harry a little because he does care for him. When Sharkface attached Mac's pub, wasn't he particularly angry with Mac? If so, it could be because he knew what Mac had done (helped create Harry) and was pissed about it.