No, they never kissed. (Unfortunately.) In my opinion, they had little crushes on each other. But for the most part, they were simply very close. I think the reason they weren't very 'sentimental' to each other was that that's simply not in their personalities. Aqua is a naturally very austere and responsible person, while Terra is callous and a bit impassive (occasionally). I don't think Terra really thinks about romance at all, and we all saw how Aqua reacted when Zack asked her out on a date. Neither have any experience with anything but a friendly love, and therefore don't want to let each other know. But I think we all saw the fond looks they gave each other in the Castle of Dreams, but whether those were just that or something a little more is unclear. They're like schoolchildren in a sense that they are so new to the concept they don't know how to handle it. Aqua's feelings towards Ven are strictly platonic. She was never 'on his nuts' or anything of the sort. She is fiercely protective of him and loves him like a little brother. When they first met, you could see Aqua's concern for him, as she sent Terra down to check on him. She also watched over him when he was in that coma, and toted him on her back to the Land of the Departure. I think when she first saw him she instantly felt a maternal instinct, and through the years that grew. You can tell she's very gentle and affectionate with him, and that's most likely because that she is so protective of him she won't even let herself be harsh to him. She has different bonds with both of them, but they are equally strong. I think the same goes for Terra as well; he kind of 'likes' Aqua but he also loves her to death as a friend, and he's protective (though not to the extent as Aqua) over Ventus, like a big brother. I think Ven is actually only capable of anything up to a sibling-like love; he's just too innocent. But his little kid crush on Aurora was freaking adorable.
