Cinderella had two

Usage examples of stepsisters.

But years of experience told: She kept her voice low enough that her stepsisters, hovering in the hall, barely heard her reply.

It would have been amusing to open that door and see her stepsisters fall in.

Prince holding one of them as though it were a rare rosebud, gazing at her with wide, awed and adoring eyes, while her stepmother and stepsisters stood against the wall gnashing their teeth.

My brothers always picked on me, and my stepsisters always picked on me.

The wedding feast was all finger food, passed around by the four new stepsisters, who had helped their mother make it.

The old fairy-tale theme of the wicked stepmother and stepsisters is relevant here.