So after reading the transcript, I saw a comment talking about Gavilar being “of his family” with the person the stormfather was referred to being Jezerah, which is a valid point. It would explain his presence there and the reason he took to drink as none of the other heralds seem to have to taken to addiction if he had to watch an entire lineage of his for old and die over and over, and how he took to talking to Dalinar.

My thoughts on this is that I think he is talking about The Sunmaker Sadees, the original conquerer of alethkar as this is the only true knowledge we have on the Kholin lineage. That his goal for conquering was driven by the storm father, that his weapon was named oath breaker because he heard the truth of the recreance, we can already see how the stormfather has changed his approach comparing Gavilar to Dalinar how even though he lied he seemed far more nuanced and open with the information he provided (and correct me if am wrong but I don’t ever remember the stormfather appearing human shaped to Dalinar only as a face and voice). The stormfather was just as ornery but he took a softer more human approach to Gavilar as opposed to Dalinar, I think the stormfather tried first with Sadees, it’s why he decried the hierocracy for having visions as he was the only who was receiving them, and why he claimed that he had divine providence (this is a weak part of my argument for obvious reasons), but was driven more and more zealous by the visions sent to him by the stormfather to unite them. I think Sadees internalized that he needed to break all cultures into being set to alethi standards, as he saw them as the only culture system that could work in the face of the desolations, and seeing the radiants as this powerful bright eyed force might have reinforced his idea of eye colour caste.

The stormfather would rationalize these cullings, given his view of life like during the storm, as the destruction before renewal as brought by the storms, but would still feel the guilt and shame of these actions which lead to his more indirect approach with the comment regarding the heralds betrayal. Perhaps besides being bitter at Dalinar the reason he’s so harsh with reminding of his failures is because he feels he must do this to keep Dalinar on track to not veer into supremacy or delusions of grandeur.

The biggest gap that I can see in my theory is that after some wiki diving the 10 sons of Sadees became the high princes so that could be a lineage stretch as it were, but it would be easy to say that the stormfather wouldn’t be too bogged down in things like that.