That was sooo funny. I remember my little brother had a little sore on his penis from playing with it so much.
My DD humped my little guy a week or so ago. Its pretty unnerving but haven't seen it since. I recently read that because they are so focused on potty training....everything kind of stems from that. Like, my DD is constantly talking about pooping and farting...we call it a buggit...anyway, she's like, "I buggit on your face mom".."I buggit on your butt, your boobs, etc" She sounds real nice doesnt she?
Anyway, I guess they are just figuring out the whole private part deal and have maybe figured out that they feel pretty good. If she humps the baby again I'll just be gentle but firm and say. "no, thats not appropriate, we don't do that." Good luck!!!