Well, as for Lightning and Hope,
Ending SpoilerLightning continues to support Hope, since her mother didn't come back. Hence, a good bond.

Hmmmm, I think Sazh likes Vanille a bit too much. Vanille occasionally appears in Sazh's flashbacks. In his flashbacks, Vanille never really existed. Why? He thinks about her, so she gotta pop up every once in a while. Normal, right?