There have been questions as to the role of baby Jacqueline and whether or not it is possible that Jacqueline, Arvin and Emily's daughter, is alive.
We have to view Jacqueline as a motivator. Her character, though very minor in the grand Alias picture, played a large role in getting Sloane to fall into the wrath of Rambaldi. We had to understand his obsession, we had to know why he became infatuated with the prophet. And as we found out in season 4, Rambaldi filled the void that Jacqueline's death left in Sloane's life. Sloane wanted to learn as much as possible about eternal life, life free of death and disease, to protect himself and Emily from further loss.
This void would later be filled by Nadia, hence Sloane "dropping" his obsession with Rambaldi to persue a relationship with his long lost daughter.
Jacqueline died. She is dead. She was born with complications, as Sloane tells Emily that Jacqueline fought to stay alive. If she were not dead and if there was a possiblity of her being alive, Sloane would have searched the ends of the earth. He would have never become obsessed with Rambaldi, but rather he would have been obsessed with finding Jacqueline. Jacqueline was merely a motivator, a piece of the puzzle that explains Sloane's actions.
To clear up any further confusion involving Jacqueline- she was supposedly born in Italy, here Sloane and Emily spent many years away- during the time in which Sydney was growing up.