"Well, you should be surprised. Because it's never mentioned in any books, Apocrypha or otherwise. But there were some angels who took humans as spouses back in the day - that's how we wound up with Nephilim. Some of them bonded with their spouses. The short version is the angel scribed their name on a human soul and left a bit of grace behind to forge an eternal bond." Gabriel absently traces a finger along his arm and chest as he explains. No one had even spoken of a bond since the Nephilim pogroms - and Dad knows he'd done his share to try and hide some of those poor kids away.