Incest Social Bug?

[Sarda]

So I have a odd situation with some of my current colonists. I noticed the same 4 people kept getting in random social fights and at first I just thought it was the pair of married sisters that I found in cryo in the ancient evil building but then I noticed there was a 2nd Incest couple between 2 brothers I purchased from pirates completely by random chance. Oddly I check their social tabs and both of the pairings have a -15 base with each other for Incest. The exact same type that they themselves are currently practicing, sibling/sibling. Is this intended? I mean, shouldn't this be the exact opposite and give them some common ground to bond over?

[Toast]

There is no incest in Rimworld between human pawns, only animals. If you're seeing this behavior (and apparently a social debuff to go with it?) this is added by one of your mods.