Dwarf Fortress has long had babies, but if you're using the recent Steam release and its sprite art, they look like adults. That's going to change soon in what Kitfox call their "cutest update ever", which will add baby sprites for every creature in-game, from aarvarks to dwarves to troglodytes.
"Every living thing will be getting a baby form (and in some cases, child forms)," says the update post on Steam. The idea is to make it easier to identify at a glance whether a room is full of children or grownups. Currently child dwarves are shown as adult dwarves with red shirts, which presumably makes it harder to, say, quickly decide who you should send to close the fortress's gates when enemies approach.
There are a couple of examples of child sprites in the post. Here's one:
Dwarf Fortress creature sprites are already small, so you can't exactly just make them smaller to indicate when one is a child. I like the approach above, which seems to be, "make them adorable." Gorlak is a cutie pie.
There's no ETA on the update yet, but they'll know more about when it's coming "in the coming weeks."
Dwarf Fortress has been a huge success since it launched on Steam, selling half a million copies in just a few weeks and generating $7 million in revenue for Bay 12 Games. Since then, they've hired a new programmer to help with the project and have been bringing more features to the Steam release, such as Arena mode.