Daily, I'm amazed by the things you DO NOT have to teach children! Yes, there are many things that must be taught, over and over, like 'share with your sister!', but they really do come excellently hardwired. Examples:
I love that you do not have to teach a baby to laugh! It just happens...and it's uniquely theirs. Lauren rarely just lets go and LAUGHS but she giggles a lot! Kate on the other hand, straight-up chuckles. It's all hers, I laugh entirely too loud, Dan has a silent laugh when he really means it...Kate's got her own thing going on.
You don't have to teach them to fend for themselves. We are born self-serving, selfish creatures. They share a banana every morning - bite for Kate, bite for Lauren, bite for Kate, etc. I hold, they either stand right at my feet and mean business, or else take a bite in between playing. BUT, when it gets close to the end, they know it. They fight for the last bite, every time.
At this age, you don't have to teach them to wave or smile at people who are being friendly (or minding their own business, or wishing that the baby would quite waving at them). These two have never met a stranger (from a distance) and love to make friends wherever they go.
Surprisingly, but here's proof, you don't have to teach them to eat a variety of foods...that vegetables are good for you! (They open the refrigerator themselves now, and when being super sneaky, help themselves...this morning, to tomatoes.)