I teach first grade and have been wondering the same thing! I just don't know how to bring it up.
aww :) you could play a game maybe something like that? lol
Maybe have a treat day and somehow incorporate a baby theme into it and ask them to find the relation ship...or a scavenger hunt one afternoon.
Do you have idea of a baby treat I could use???
Baby carrots... Baby cupcakes anything miniature sized.