Something that made BioWare games unique for a long time was the fact that your protagonist could woo some of her/his companions, thereby giving extra depth and immersion to the interactions you could experience. Of course, due to the fact that gaming used to be a largely male-dominated sphere, romance options were heavily biased towards the straight male player base back in the day, and it’s only recently that things have started to evolve. Thus, in Baldur’s Gate II, the romances are still very vanilla, both in terms of choice of partners and in terms of the actual romance progression (marriage and/or children are involved in almost every case, Evil = promiscuous, etc.). Male protagonists can choose to pursue Aerie, Jaheira or Viconia–representing the Good, Neutral and Evil outlook, respectively–, while female protagonists are stuck with the nightmare that is Anomen. I also have to ask: what’s with the female elf fetish?
That being said, there are certain restrictions to keep in mind. You see, the characters have their preferences as well. First of all, if your Bhaalspawn is a dwarf, half-orc or female gnome, you can forget about romance altogether. That’s…a bit discriminatory, to be honest. If your Bhaalspawn is human, half-elven or a halfling, all choices are open, depending on gender, of course. Viconia doesn’t like male elves, while male gnomes can only romance Aerie. Because of…Quayle, I guess. Creepy. Anyway, as far as I know, alignment won’t outright prevent your Bhaalspawn from striking up a romance, but s/he may find it impossible to a) keep the character in question in the party and b) reconcile what s/he needs to tell them to progress their romance with her/his worldview. The only two instances where this isn’t a problem are Viconia and Anomen, since their alignments can be changed. Also, it might go without saying, but kicking your Bhaalspawn’s chosen partner out of the party will bork the romance (this doesn’t apply to the several instances where Jaheira has to leave because of Harper duties).
Aerie: A pretty straightforward romance, except for one specific conversation, and provided you don’t factor in Haer’Dalis. Aerie is obviously damaged, both physically and psychologically. Losing her wings was a dramatic change for her, and being ground-bound after having experienced flying (and, as an elf, even young, she would’ve been able to do this for at least a century) is extremely difficult to come to terms with. It makes her feel ugly, purposeless and despondent. Consequently, your Bhaalspawn should be ready to reassure her. A LOT. Frankly, not only does it become extremely annoying, but also somewhat uncomfortable, because I don’t actually think that she’s ready to deal with a relationship in her mental state; I mean, her sense of self-worth is somewhere in the negative digits. Keep in mind that comforting her should come first, no matter what she says or does. Fair warning: she will get pregnant and give birth in Throne of Bhaal. Yes, you’ll have to carry a baby around. Yes, it’s very awkward. And no, you don’t get a say in what she names him, which makes no sense. As already mentioned, if you insist on including Haer’Dalis in your party, he will woo Aerie as well. He may even succeed, despite the fact that your Bhaalspawn is romancing her. Ultimately, however, she will leave him, as his nonchalance will make her feel that he doesn’t really care about her, but that doesn’t mean your Bhaalspawn will be able to get her back. Another thing worth noting is that, if both she and Jaheira are in the party and both are still potential romance candidates (i.e. you haven’t locked in their romances), Aerie can be downright vicious with her comments, which is somewhat surprising, coming from her, and makes me like her even less.
Jaheira: My favourite romance of the lot, but also the longest and most complex one. Unfortunately, in the vanilla game, it’s also hopelessly bug-ridden and has a high risk of breaking if you don’t use a mod to fix it. In fact, I’m not even sure it’s possible to complete it without doing that. Anyway, as anybody who has played Baldur’s Gate will know, the problem with romancing Jaheira is that she’s been happily married for several years and is freshly bereaved when the game begins. I was actually afraid that the romance would cheapen her history with Khalid, but, while the mourning process is shorter than what I would realistically expect it to be (for obvious practical reasons), it’s also far from instantaneous. She needs time to grieve and move on, and even once she does admit to feeling attraction for the protagonist, it takes her a while to reconcile with her loss. Her personal questline doesn’t make things easier for her either. For a character who’s supposed to be all about balance, there’s a whole lot of imbalance for her to deal with all of a sudden. And yet, despite all this, she manages to remain dignified and true to her no-nonsense, somewhat crusty and bossy, but good-natured self. I would say that this is the only romance where the Bhaalspawn and their partner truly feel like equals, which is what makes it so satisfying. As an aside, the BG novelisation–as shitty as it reportedly is–also includes a romance with Jaheira.
Viconia: Romancing Viconia is a rough ride. Keep in mind that, although she frowns upon purposeless violence, she doesn’t outright disapprove of drow society or customs. She respects power and believes that men are lowly creatures only fit to obey a woman’s every whim. Therefore, wooing her is a war of attrition, where your Bhaalspawn will have to repeatedly weather verbal abuse and being pushed away without seeming weak, all the while confirming his interest in her, and, even after she does ‘give in’, her circumstances as an outcast mean that she’ll never be entirely at ease with the relationship. The thing is, romancing Viconia is the only way to get her to open up about her past, and once you do hear about it, you realise she has just as many issues as Aerie, even if she deals with them very differently. I’m not entirely sure just how well-advised a relationship is in her case, either. It’s certainly more interesting, as she has a far stronger personality than Aerie can ever hope to have, but do make sure that your Bhaalspawn also keeps her needs in mind. If he’s Good or Neutral, it’s possible to change Viconia’s alignment to True Neutral (not sure how that jives with her patron deity), but you may also romance her with an Evil character. Finally, a fair warning: ask yourself whether someone who’s being relentlessly hounded by an Evil goddess really has a chance of ever settling down peacefully. Hint: they don’t.
Anomen: I hear that, originally, BioWare were planning to make Haer’Dalis and Valygar romanceable as well. Why they decided to remove those options in favour of Anomen, of ALL people, mystifies me to this day. Not that I particularly like Haer’Dalis or Valygar, but they would’ve been better choices. There are no surprises here: Anomen is arrogant, prejudiced and attention-starved. He also has a really creepy tendency to compare your Bhaalspawn to his sister and has some sexist moments too. And if you’re expecting him to change, you’ve got another one coming. Your Bhaalspawn, on the other hand, is expected to accommodate his ego every step of the way. Sure, you may understand where he’s coming from, what with his family issues and all, but, even factoring that in, he has the best circumstances out of all the romance options, and yet, only Aerie surpasses him in sheer whining output. And, at least, Aerie doesn’t belittle your protagonist or gab about how awesome she is all the time. There are no alignment issues with Anomen, since you have control over what he becomes. The only problem is that turning him Chaotic Neutral leaves you with a crappy healer on your hands. Ultimately, there’s no incentive I can think of for romancing this guy, except that he’s literally the only choice a female Bhaalspawn has. But hey, that’s what mods are for!