The mystery of sisters.

I'm working and the girls are singing.

This is a welcome change from their usual routine, which as of late has involved shrieking, stomping and fits of whining. They're playing a game I don't understand, and that involves dancing and singing a song about being sisters. The only downside is that Grace is singing in an ear-splitting soprano that is not exactly on key.

Grace and Lauren are mysteries to me. Virtually every day on the way home from school they get in a fight in the car. A fight about nothing. I understand it - they're tired, hungry, ready to get home and get into pajamas. I feel the same way. And I suppose that's the difference between adults and children, that I can feel that way yet somehow dredge up the energy to try to distract them with questions about who they sat with at lunch and what was the funniest thing that happened today. Honestly, some days I'd like to whine and moan just as much as them. But on the worst of those days I just pull over the car and wait for them to finish. It's either that or start screaming, which I'm working on not doing.

Work has been so busy these last few weeks that I'm quite sure I've been phoning it in on my mom duties. But no one seems to be suffering. Much. I'm working harder than I've worked in a long time, and it's good work. The kind where I'm learning new things, making lots of decisions and challenging my brain every day. The only bad thing is that by the time I get home I feel like I've taken the SAT for eight hours.

But somehow dinner still gets on the table, everyone seems to have clean clothes and I haven't forgotten to put anything critical into a backpack. And looking at the way they are playing together right now I think that it's not a bad thing for them to be out of my laser focus. Instead they are focused on each other, creating an imaginary world that - and I'm not kidding here - has moved Lauren to tears.

"I'm happy cwying, Gwace," she said just a minute ago.

So what's so mysterious about sisters who love each other one minute and want to kill each other the next?

Nothing I guess. It's just the way they are. Either way they're sticking together, which makes me feel like we must be doing something right.