It's almost Raelyns birthday?

I haven't had a baby (object) grow up on their own when I have aging off (note, this is before I got and installed Growing Up expansion), either in my own household or in other households I don't play or not playing at that moment (I have aging off for all except household I am actively play in).

But maybe it is part of the Growing Up? Maybe because of the infant stage they have the object babies grow up on their own to get to the infant stage? Just an ask because I haven't played with infants much and the only infants I do have at the moment I aged up the 'baby' stage myself to get to the infant stage.