So Firstborn woke up before we did, at around 8:00 this morning. He apparently looked around the house, realized that we were still asleep, and went into the kitchen to play quietly. (Or at least "quietly" as perceived by a six-year-old.)
I heard this from the depth of my warm, snuggly blankets and thought, Oh, good. I don't have to zzzzzzzzzzzzzzzzzzzzzzz.
A little while later, my brain surfaced again briefly because I could hear Secondborn crying. Under the circumstances, this probably just meant that he was now awake, too. As I was lying there contemplating the tragic process of actually climbing out of bed, I heard Firstborn say, "It's okay, Secondborn. Do you want to bring your weeeoh-weeeohs  into the kitchen?"
My relief was only overshadowed by my snoring.
Later, I overheard a brief exchange in which Firstborn asked if Secondborn wanted to play with... something, a car I think. Secondborn replied that he wanted a balloon ("boon!") instead. So a minute or so later, I hear the distinctive pphphphphphpphhphphphphphphphphphphphbt sound of air being let out of a balloon. The only way that could be happening is if Firstborn had actually blown up a balloon himself, for the benefit of his younger brother. The sound reduces both boys to helpless laughter.
Beautiful Wife got up a few minutes before I did and found the boys playing together. All told, I think we got an extra forty-five minutes of sleep. Which was completely wonderful. And, well, our boys like each other! We must be doing something right.
 Secondborn has an extensive vocabulary for a two-year-old, but it's a rather idiosyncratic one. Beep-beeps are cars. Weeeoh-weeeohs are firetrucks or ambulances, or any vehicle that sufficiently resembles a firetruck or ambulance. All buses are school buses. Oh, and all bugs are wa-wa-pedes.