I thought he was her natural father??? Though I cant see those two together...
Edited: You're right. From Wikipedia
According to Danielle's descriptions: When she and her crew shipwrecked on their route from Tahiti, there were six total who survived, including a pregnant Danielle. The rest of her team eventually died in an area she referred to as "the dark territory," including Montand, who lost his arm, Brennan, who "took the keys", and Robert, her lover whom she killed because he had "the sickness". Danielle eventually gave birth to a baby girl she named Alex. Alex was then abducted by The Others soon after.
Maybe Alex knows but as Ben has raised her, she considers him Dad?
I thought the last episode was rather anti-climatic....I wasnt too interested in Michael anyway, though it answered some questions.