I don't know if anyone's brought this up before or not, but for the past... many versions actually, maybe even past year or so, I've noticed a particular bug with multibirths.
If a girl has more than one child and they are not all girls, the game has this weird tendency of automatically making them all girls when they come of age. I don't have a log, and I'm not actually sure how to log something like this, but its extremely easy to reproduce.
When I first noticed it, I shortened pregnancy and weeks until grown times and increased multibirth chance, and found that it was a thing that consistently happened. I had initially thought that it had something to with the fact that I had decreased the chance of girls being born to something like 25%, but the problem still existed with 50%
Its really a consistency thing that annoys me alot, and I never mentioned it before because I figured it had probably been found and would be fixed eventually, but it wasn't so... uh... yeah, I'm just mentioning it now, in case its not a known bug.