sorry if this has been asked before but will eternum also have incest/harem like oial
He can't answer that to avoid issues with patreon. Unfortunely patreon is pretty strict with that, and probably doesn't want to risk patreon mods roaming around. I even recall many people here (myself included) telling to remove the Iris poll on patreon, to avoid issues. Yes there is SubscribeStar, but the number of supporters on patron atm is way larger when comparing to Subscribestar.
We didn't get more teasers about the story and characters of Eternum yet, but my guess is that if it fits the main theme, then it may exist a patch. Oialt also didn't have at start, was made due popular demand. While I love incest in games don't get me wrong (the more the merrier, I love taboo and corruption stuff), but it must fit the story.
Being family members for the sake of being family members isn't an healthy direction when developing a story and can create issues when creating a plausible plot. After all, that creates one more condition to take into account for a believeable love relationship.
All I know is that the game will surely be fun to play, with or without it. I just wonder how it will be better than Oialt as Caribdis says, since that game is already a masterpiece imo.