My sim gave birth to two babies, but they aren’t twins.

So, my sim was only having one baby. They gave birth to the baby, but I glitched it somehow when entering CAS right afterwards, so the game still considered my sim pregnant. Getting back into the world, they still had the buffer for being in their third trimester. So, almost a day later, they had a second baby. 

Adding on to this, the father sim doesn’t have the first baby in his known sims thing, so it doesn’t consider the baby his child. So weird.