Although it makes me sick to say this, you should probably include Sloane as an option (if you're including Sark and Will, even remoter possibilities). He DID apparently know her as Julia, after all, since she sent him the key. But I hope with every ounce of my being that nothing like that happened!!! Could anything possibly be more disgusting?
But I don't think she had a baby at all. That would mean we'd eventually have to see the kid, and an infant or toddler would NOT fit in on Alias.