Kirby is doing exceptionally well with this huge change, considering he was an only "child" for two years. He was very curious about Robby when he first got here, but now he pretty much ignores him - aside from the occasional glare from across the way when I'm holding or talking to Robby. He's even nice enough to lift his head to watch me walk out of the room for the 3am feedings.
Today, Robby actually decided to stay awake for more than five minutes, so we tried some tummy time. Kirby was enthralled by this wiggling, grunting creature on the floor, as if he'd never seen him before. I called him over and he carefully laid beside Robby on his blanket and sniffed him all over. Then he decided that Robby needed a bath. Robby didn't know what to think (I think he was still wondering why the heck I put him on the floor to begin with). I'm very proud of Kirby, though. He was very gentle with Robby and really wanted to get involved with what was going on.