Oh my gosh, my 19mo realized this week that other people have nipples. She eyeballed dh's weird because they're hairy. We jokingly asked if she wanted Daddy's milk and she shook her head. lol! We've asked all of them at one time or another, most of them have said no, but I remember #1 trying to latch onto dh when he was younger, much much younger, probably closer to 6mo.
So my 19mo is really close to my 6yo dd. She always wants dd1 to pick her up, which is not really possible. She can lift her off the ground, but dd1 is 42lbs and dd2 is 24lbs, so it's a bit much. Cute as heck to see it though! She loves to lay with/on dd1 on the couch too. Today she was laying on dd1 and pulled her shirt down (I'm a shirt down nursing Momma) and licked her! OMGosh, I about died. They were both laughing so hard. I told dd2 that her sister didn't have any milk, and I told dd1 not to encourage it. Cute and funny, but yeah, I don't really want to encourage it.
Re: She realized other people have nipples!