Major characters shown definitely having or pursuing a heterosexual relationship:
- Thancred (the womanizer)
- Urianger (with Moenbryda)
- Alphinaud (major crush on Y'shtola)
- Runar (same)
- Chai-Nuzz and Dulia-Chai (married)
- Gaius (with Livia)
- Louisoix (presumably; had kids)
- Varis yae Galvus (same)
- Bahamut (with Tiamat)

I probably missed a few. But the point is, for most characters we just don't know whose pants they'd love to get into, if anyone's.
And that's the way it ought to be, IMO.