So, looking at the Cython update, I can't help but think that the god absolutely most likely to be one of the daughters is Fury. She hits all the box's.
The daughters as broken off Aspects: protection/justice
The daughters as actual kids: is a classical god that's already connect with the family.
Narrative children: it's totally a sold human narrative that a child would be squired to her Aunt to be trained up, that's how it was done at the time.
I'm not saying everything one of those is the strongest case, but she is the only one that hits every one of the stated ways to look at the relationships between gods.
As a note to inform the people who don't know what Jyn's talking about, Fury is the Goddess of Righteous Anger and often worshipped as an aspect of Myrmidia in Estalia and Tilea, and she's recently picked up steam in canon 2E WFRP in Reikland after the Storm of Chaos. She is a minor goddess, but like the Dark Maiden I think she's depicted as an aspect rather than an independent entity, sort of like Renbaeth, Clio and Scriptisi are to Verena.
Here is the story of Fury:
"When mortal, Myrmidia drew many heroes to her side, but none are more famous than the shieldmaiden Fury. Her tale is recorded in the Bellona Myrmidia, and is one full of horror, pain and betrayal. The events of the sad story result in a young girl renouncing her name and swearing to claim revenge for all the dark deeds of the world, a task she takes to with unparalleled passion and anger. Although it pained her, Myrmidia could not bring herself to stop the girl, for she intimately understood the source of Fury's rage. Instead, Myrmidia did what she had to: she used the girl on the battlefield. There, Fury slayed and slayed and slayed, until eventually, once all her enemies were gone, she collapsed, weeping. Fury's last stand was in the Abasko Mountains. There, her body was found by Myrmidia, surrounded by piles of dead Orcs and Goblins. The site is now protected by the order's high temple.
Even though the Order of Fury is mostly comprised of women in Estalia and Tilea, in the Empire it is almost exclusively male." Tome of Salvation Page 45
An excerpt from the Bellona Myrmidia, the Book of Fury:
"And she did hear of what had happened, and she came unto Her, and she said, Because of what hath been done to thee: from this day forward I renounce my name, and I shall be called Fury."
Overall, I'm not seeing it. She's a traumatised girl who gave up everything to throw herself into combat because she wanted vengeance but it ultimately left her empty. Myrmidia didn't know how to take care of her, so all Fury did was kill untill she died.
It's a possible dark reflection of the obsessive nature of Shallya combined with the protective aspect of Ranald, but she's far more violent than either god would ever like to be.
