Season 5 told us that Charles had a daughter with someone off the Island. We know Daniel and Penny are half siblings. I think the mother of Penny is Margo Shephard. A couple things that have common ground. Daniel has always had the ability to play piano, David Shephard as well plays. Desmond me Penny "for the first time" when she was doing the tour destraught, identical to the first time Jack met Desmond. Thats not concrete but we know that LOST is huge on juxtaposition, irony and degrees of separation. If this is true I don’t foresee it playing a huge role in the story.......but you never know.