Oh shit, yeah, I said I'd give story advice. Cowboy, I'd recommend you don't bother writing for both a female and male space commander. That seems like a fair bit of extra work for almost no pay off, as I doubt anyone on here would care. The only few who would want that would be the kind of people who'd get offended at the lack of an agender option.
Oh, and thus; I wouldn't see much need for asking for the sexuality. I'd recommend rather than that, you just have them presented with the romance options later on. That way, you don't need to start your story off on an awkward note of asking for information, plus, I actually noticed that you can't play as a bisexual, which does make me wonder if I'd have my romance options limited later on because I have to pick one.
Anyway, probably a better idea just to have whatever romance options the character would be offered to hit on them or whatever, and then you can turn them down as you wish. If you're straight, turn down the character the same gender, or vice versa, or pick your favorite if you're bi. If you're not planning to do much with romance and were just going to pop in references to a love interest at home or something, no need to bother much with asking for sexuality if it's not important, no one will be bothered if the gender of their loved one isn't what they're actually into.