Kids can be so sweet to eachother when they think that nobody's around

So I'm sitting at my computer now checking my email and other random things and the kids are playing in the front room. They are actually jumping off of the couch onto the floor. They're not really supposed to be doing this and I am about to get up and remind them of this when I hear Alexander jump off the couch and upon landing say "Ouch, I gotta boo boo". This is followed by Hannah saying "don't worry, I'll make it better" and then I hear her kissing his boo boo. Isn't that just one of the sweetest things ever!?!?! They can be so great together, especially when I don't interfere. Of course, I can't let them play by themselves for too long. Eventually they do try to kill one another but for about an hour or two listening to them play is the best thing I hear all day.