Alexandra Rousseau or Alex was kidnapped when she was one week old by Benjamin Linus. He raised her as an other and his own daughter.
Excerpt from the Destroyer of Delights:
Nisrin and Amy are busy washing crates full of clothes. Amy is shocked to learn that Nisrin considers herself to be a slave and is even more surprised when Nisrin reveals that she was taken from her parents as a child, sold to the Caliph and given a new name.
They didn’t change Alex’s name but if you can’t see the similarities you will never see them.
The Destroyer of Delights: