Character siblings

Mercy has two step siblings. Sisters. Nan and Ruthie.

They're about her age and she didn't find out about them till She got sent back to live with her mother when she was 16.

Surprise! Her mom had a husband and kids! And had had them for most of Mercy's life, but somehow never mentioned them when she was visiting Mercy every summer.

And Double Surprise!! Her mom's husband and other kids didn't know anything about Mercy either till she showed up on their doorstep. Ooops.

She also has a half-brother, but he's kind of part of a major later in the series spoiler, so...