Crown

Two siblings, brother and sister, have been separated for a long time when meet up again. They soon learn that they were separated due to the fact that they were children of an ex-ruler from a small country.
High-school girl and orphan Mahiro has had a hard life after her parents' death. Now, suddenly, while she is at work, two young men push her into a car and- OMG- kidnap her! With family united again and some nasty assassination attempts, Mahiro's life changes drastically.
source: Baka-Updates Manga