A Decade Of No Sleep

It's the day after my daughter's 11th birthday and this is what's passing for homeschooling today:  I'ts now after 1pm and my daughter's gone back to bed for a nap after not being able to go to sleep till well past midnight (probably because she's been SO excited for her birthday for the past four days), and then being awakened before 4am by her brother in the room next to ours, who began to happily play and chat.  She left our bed grumpily and then went back to her room where she said she didn't go back to sleep till 8.  Yikes.  So she's back in bed while her brother, after doing some NDT and balance board exercises, is happily watching a Hillsong Kids music DVD.  He's been awake and chipper all day.  I just don't get it.  He's 12 years old and I know I should have some understanding of something about him by now, but I don't.