...is there actually anyone you would care more about than your child, though?
I would also like to point out that afaik there is no mention of Minfilia loving Thancred back - the two of them arent the great lovestory in Eorzea, by far not!
Little Edit: Also... talking about how the Scions have no real connection between each other seems rather "unfair" to me - Alisae and Alphinaud are twins (how much closer could they be? and no, please dont go the romantic route again...), Papalymo and Yda were obviously pretty close aswell and all Scions together decided to protect Lyses secret. Urianger and Y'shtola can seem rather distant, agreed - though its worth noting that Uriangers "connection" was killed before we had a chance to properly meet her...
All in all I have to say that I prefer the connections - or the lack of connections - between the Scions over some forced love-story. Seriously, Thancred decided to raise Minfila after it was basically his fault that her father died. It would have been pretty, pretty weird if they'd actually fallen for each other and went on to develope a romantic relationship. Seems kinda wrong to me - "Alright, I raised you like a daughter, but now you're 20 years old and therefor old enough to do... other stuff with me!" (And the other way around - Minfilia suddenly turning her "father" into a boyfriend seems equally wrong).
I got the impression you missunderstood why Thancred misses her so much: He feels that he failed her and wants to make up for it. He doesnt want to marry her...