I could replace the same trait opinion bonus for gods and demi-gods with a same religion opinion bonus. For demi-gods, I'll probably lower it a bit since it affects a lot more characters (I'm not worried about balancing gods).
Hel, Loki, and Sliepnir are generally considered to be part of the Norse gods (well, Sliepnir is more Odin's horse than a god). In Norse mythology, there is a lot of intermarriage between the Aesir, the Vanir, and the Jotnar. For instance, Skaði, the Godess of bowhunting, skiing, and winter, mother to Freyja and Freyr, was a jotunn. I'm generally putting characters who were considered gods in Germanic and jotnar who were enemies of the gods in the Jotnar religion.
I'll have to check why you were able to convert a goddess - I've been trying, piecemeal, to block gods from converting to monotheistic and non-theistic religions.