I started a legacy attempt right after the patch. The first pregnancy resulted in only one infant, but the second turned out to be triplets! There was no fertility award involved, either. So single births are still possible, but they might have changed the chance of multiples. It could also be statistical blips, like getting a lot of one gender or the other.
Oh, the triplets are identical, and 2/3 of them aged up with the same hairstyle as their older sister. I normally just go with whatever the game randomly assigns to children, but I needed to change hairstyles to tell the four girls apart. The older sister has a different face and eye shape, but the same hair and eye colour, as the triplets.