I think that Terra is great by herself, considering her level of maturity, and mentioned asexuality. I mean, consider the girl's thoughts and emotions for a moment. A) She's not too long ago been released from a device that robber her of memories and caused her to wreak havoc, she's been half-esper and half-human, confusing enough on its own to give her a lot more questions than relationships to think about, added to that her recent Lack of an Esper side, and she might not have had so much time to form a real relationship admist so much fighting. When she Does get a break from fighting, she instantly makes a close connection, albeit with children, but that's who was there.
Agreed about her taking the role of a surrogate parent/needing/wanting a family relationship. Sooner or later, though, i think the human side of her would catch up with her. She might remain single, but I wouldn't place a bet on it.
As for potential mates, then, I'd say someone not introduced in FF, Edgar (Am I recalling correctly some meaningful conversation between the two, Terra laughing at him, and Edgar becoming so much less of a womanizer, egoistic, etc over the course of the game?), or Sabin. Though, honestly, I have a hard time seeing Sabin. They're too buddy-buddy, in my mind, to be in a relationship.
Sabin's just too odd for her, anyway, I think. He's much more brother-in-law material for her.
Consider, also, the similar situations/duties that Edgar and Terra have. Edgar has to watch over a whole kingdom of people that he cares deeply for. Terra has to watch over the kids. Both are reluctant to leave and fight for their respective dependants. Both have somewhat of a separation complex (If you remember, Edgar didn't Want to be king. Terra likely didn't Want to be left behind from her family & Esper people.), and both were reluctantly allied with the enemy (Terra by force after flaming the troops, and Edgar by force for fear for his people.). More or less, they can relate to one another.
I can't see her relating to Setzer, Shadow/Clyde, Cyan, etc. (Well, she and Cyan are kind of the last of their people, but even so.)
Also consider age differences. Terra is 18, Cyan is 50, Edgar, Sabin, and Setzer are 27, Shadow must be rather old, and Gau is only 13.
With all of this in mind, it's harder to see Terra with any of the main characters. Even if we apply a rule like "Celes and Terra actually are almost 19" and "Locke Just turned 25, and the three others Just turned 27.", we still come up with some distant age differences. Celes and Locke obviously happens, despite the 5-7 year age difference, but Terra and any of the other older males comes to 7-9 years of difference! This just makes it a stretch, to me, to see Terra with one of these other characters. It's still possible for Terra and Edgar to happen, due to their common circumstances, and that's what I'd favor if I HAD to choose someone, but.. I think I've said decent enoughfor now.
Review what's said in game, and consider that, as well.
