Blogger Brittany e-mailed in with some more information on Nadia and whether or not it is possible that Jack is her father and not Sloane. Brittany wrote:
"Toward the end of season 3, Sloane makes the comment to Jack that as long as he and Sydney are alive nothing else matters. I think that Sloane used Jack to find the location of the Passenger. Rambaldi would only reveal her location to her father, and when Sloane broke the hourglass and activated the brain wave device Sydney and Jack were there with him. I think Sloane has known all along that Jack is Nadia's father, but has used Jack and Sydney to fulfill Rambaldi's endgame."
I think Brittany makes a very valid point, but I would like to take it a step further. It is possible that Sloane manipulated Jack and Sydney into believing that Nadia is Sloane's daughter. Perhaps all the information about only the Passenger's father being able to know how to find the Passenger could have been made up in order for Sloane to follow through on Rambaldi's end game. Sloane had to make Sydney believe that he was the only one who could find her sister. And Sloane knew Sydney would be mad at Jack if he didn't somehow prove Sloane innocent and prevent him from being executed. He knew Jack would save him and that together the team would search for the Passenger. Perhaps both Jack and Sydney could have read the green goo from the hourglass if they knew what symbols to look for or how to read it.
Sloane then uses Nadia as an explaination for why he has given up Rambaldi. It is a great cover, considering he supposedly lost a daughter which threw him into Rambaldi in the first place. Furthermore, we know Sloane has always had a soft spot in his heart for Sydney and he told Dr. Barnett that he hoped her determination and strength had come from him. Nadia might be fulfilling some sort of personal prophecy for Sloane; he has always wanted a child- and the fact that Nadia is linked to Rambaldi is even better. This would explain why he has invested so much in protecting her and searching for a cure- unless Nadia needs to be cured in order for Rambaldi's end game to be revealed.
Also, we have to take into account all the ambiguous lines and looks between Sloane and Jack and Jack and Irina, which would lead us to believe that Nadia could in fact be Jack's. I don't believe the writers would have mentioned the possiblity if they didn't wanted us to doubt Nadia's paternity.
What do you think? I know we have discussed this before, but I think Brittany cast a new light on it.