My wife's family were wealthy Chinese near Hong Kong. Her grandmother took in a poor girl as a servant. She was part of the family but also basically a slave. The grandmother arranged her marriage when the girl was older. We met the girls granddaughter when we visited china - she was a new college student. The two families still think of themselves as related.

Almost same story (except china), my grandmother lost her parents very young. A family took her in and she worked for them until 20 years old or something then she got married.