Hermione Granger

"Probably not," Elle says thoughtfully. "I mean, my mom is not one to keep details to herself, so she'd definitely have mentioned if I had a twin. But maybe you and Caroline. We could all be sisters." Steph is a real cutie, and it's not beyond belief that she might have sisters somewhere. Maybe her dad had kids he didn't know about before he got married, but the timelines are all screwy because of the whole weird multidimensional thing. She's heard a couple people call them doppelgangers, but that's not the only possibility.