It was the sibling thing, I suppose. I was fascinated by the intricate tangle of love and duty and resentment that tied them together. The glances they exchanged; the complicated balance of power established over decades; the games I would never play with rules I would never fully understand. And perhaps that was key: they were such a natural group that they made me feel remarkably singular by comparison. To watch them together was to know strongly, painfully, all that I'd been missing.