Well, I have an opinion on this that has nothing to do with story plots.
I think that Victor Garber and Jennifer Garner look enough alike to actually be father and daughter. With all the deliberate actions taken in the making of this series, it would be hard to believe that they "accidentally" cast two people who look enough alike to seem related.
Add Lena Olin into this mix, and you have a trio of completely unrelated people that could easy pass as a family, just on looks alone. Add in the mannerisms (Irina and Syd's hair adjustment, Jack's permanent brow scrunch that Syd does once in awhile), and it's something that would be completely senseless to tear down.
Back on plot track, I completely believe that Sloane is at his manipulative best. He sees everyone as pieces on a chess board, and he is the chess master. This is something thrown out to achieve a certain goal, even if that goal takes years to realize.
Sloane is very practiced, and very good at waiting a long time for his plans to come to fulfillment.