there are three siblings. one boy and two girls. she'd be the middle sister. they were born in england but sent to live with their mother's sister in bar harbor when they were still children. she would have been anywhere from 6-8 when that happened. there are some more family details if you're interested in that line.
the nanny would be a new hire. he's recently acquired guardianship of his youngest sister's daughter and he has no idea how to parent. they're living with his elderly aunt who can't be responsible for a toddler, so the nanny would be live-in. we'd either start with an interview process or say she was just hired. whichever you would prefer.