Fantasy read in 2000's, Romeo and Juliet like love between characters that are forbidden to be together bc the last time 2 of these different religious sects were together their child nearly destroyed the world. Spoilers.

[Bethani M. Dugan]

The 'main' land is divided in to 7(maybe) different religions. Intermingling is forbidden between these one group of preists and a different group of priestesses bc however long ago that it had had happened in the past their offspring was some kind of abomination that exuded sunlight like beams that literally broke the world. The two mains don't realize they are from the forbidden sects until after they fall in love. When they find out shes pregnant he goes on a quest to maybe beseech the gods to not let their baby be an abolination and has to go througb trials, maybe. She gets left to have the baby alone. While they are doing all this, the land is also being invaded by the ppl of the north that are like ice related or just really like cold or something. The end is very much a ton of stuff happening all at once. The boy doing the trials. The girl running for her life while in labor. The land/city being actively invaded. It culminates in the girl having twins, thus no abomination, but still dying. A midwife running off with the boy. The leader of the ice ppl finding the girl in a tree in the forrest were the midwife(maybe) left her and taking her home bc he always wanted a baby girl. Pretty sure the priest boy dies from the trials. Read in the 00's when i was reading similar stuff like wot, robin hobb, and the like.