Syd would freak out. Jack would go through an existential crisis, because his Doing It All For My Child rationale depends on only one child being around, not two with possibly conflicting interests. Anakin, otoh, would not really have a problem, save for the part where he wonders why his mother got the slave on Tattoine lot while Sydney's got the glamorous SpyMom existince.*g*

(No, seriously, I don't think Anakin would have any incest taboo problems with relatives he hasn't grown up with.)