This is the cutest reaction to thinking about the Facts of Life for the first time EVER.
OMG, this kid is freaking cute. He is baffled, excited, perplexed, excited, confused about how a baby could be in his mom's belly, excited! The great thing about kids is they're not super amazing actors. Even Dakota Fanning was just "meh," let's be honest. So you know his joyful wonder over having a new sibling coming into the house, to share his bed and to tell his teacher about, is very, very real.
Also, shout-out to mom who confirms fifty times that the baby is in her belly, then skirts the real issue of how it got there. Though that video would probably be adorable, too. Great kid, mom.