Email this morning:
Brother: good morning. now you're three years older than me, so I guess that makes you boss, at least for almost two months ... when you go back to only being two years older than me ... and still big sister ... but slightly less so. one of these days I'm going to catch up, though, and when that happens you'd better watch out.
Me: Yes, well, you ARE catching up. Right this moment you are 93.75% as old as I am, whereas one year ago you were only 93.61% as old as I. It's only a matter of time.