@Alien Not quite.
Spoiler!
We don't actually know if Glorym is Sovieshus daughter or not, as there's evidence to both (however I personally believe she isn't). Regardless, Ergi's reveal was primarily to further his revenge on Sovieshu by messing with his head, and his internal monologue regarding it is dodgy on whether or not he was actually telling the truth. As of the novels current state, there's been no confirmation to whether or not Ergy was lying