I'm having genealogy issues.
I have three girls from the same parents, but it lists them as half-siblings. Not only are they all full blood siblings, but two of them are twins. They have one half-sister, who doesn't live with them anymore.
Granted, the parents are siblings (shush), and impregnated eachother. So I guess you could make an ass-backwards argument that one of the three is a half-sister, since technically the mother and father are different, but that doesn't explain the twins.
I'm more than a little disheartened. I opened the relatives box and expected to see "twin sister," thinking "aww, we get to have Christmas with twins." Then I got sad. I'm not code-goblin enough to find out for sure if it's a base game issue, but reporting it to Maverik is almost certainly a waste of time anyway.
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You don't need to have experience with the code to figure this out. I know it takes time but if you simply played the game without mods, then you would find that Strive 1.0d does not differentiate siblings from half-siblings; there is only one category for all siblings. Also vanilla Strive does not have multiple babies per birth so twins never happen. If it was a problem in vanilla Strive, then the Bugfix mod or the Strive Discord would be the proper places to report it (mostly to me).
The relation of the parents to each other is not relevant. Note that it is possible for twins to have different fathers if the mother has ever had sex with more than one person with a penis. There have been several bugs related to semen lasting potentially infinite amounts of time within the womb. Additionally, if the father left the mansion, never existed, or ceased to exist before the children were conceived, then the game would generate random temporary stand-ins to provide the necessary data to create the babies. Therefore I recommend verifying that the characters indeed list the same father in their relatives data. You may provide the save file for review/fixing either here(through a file download service) or on Discord.
I'm not aware of any attempt to track twins in the relatives data, which is most likely due to the significant increase in complexity required simply to attach a different name for sibling.