Chanakya

I was the big, bossy older sister, full of enthusiasms, mad fantasies, desperate urges to be famous, and anxious to be a saint - a settled sort of saint, not one who might have to suffer or die for her faith.

The historical novelist has to consider what has actually happened, while the SF writer is dealing in possibilities, but they are both in the business of imagining a world unlike our own and yet connected to it.