Khalid and Jaheira are hangin out in the Friendly Arm Inn, you know this because Gorion told you before he kicked the bucket. These two are my favorite pair, meaning, I don't mind not being able to split them up. If you refuse their offer to join your party, they'll rebuff you from that point on and won't join your quest, ever, end of story, kaput! This is very bad, because Khalid is the best fighter at this point (Monty's okay, but he's well, evil ~_-), and Jaheira's not bad with a stave herself-plus, she's a druid, which means she can cast curative magic. One of the first things you should do, is find her a sling and buy some bullets, likewise with Khalid, slap a bow on him and make him an archer. (Also bear in mind that Khalid is the only non-evil fighter that you can give 5 proficiency slots to.)
If you wanna have a brawl, then keep these two with Xzar and Montaron. Chances are the four'll throw down the guantlet and start taking shots at each other. This is a bad thing, because there's nothing you can do but stand there and watch as they kill each other off. This happened to me in the Nashkel Mines, so my word of warning concerning Khalid, Jaheira, Xzar and Montaron is to seperate them as soon as you can, I usually wait until I get to Nashkel and drop off the evils. If you need, or want, to get rid of them before then, you can replace them in Beregost and still get to Nashkel with a full party. (However, I do not suggest picking up Kivan just yet)
Vital Statistics:
Khalid
Race: Class: Alignment: Half-Elf Fighter Neutral Good
Strength Dexterity Constitution Intelligence Wisdom Charisma 15 16 17 12 10 9
Jaheira
Race: Class: Alignment: Half-Elf Fighter/Druid True Neutral
Strength Dexterity Constitution Intelligence Wisdom Charisma 15 14 17 10 14 15
On a side note, these two can be amusing to have in a group, particularily if you've got an evil other than Xzar and Monty. (which, btw, you'll find out what makes each pair so hostile to the other later on in the game as part of a side quest) They even share a few tender moments while within the group ~_- such as Jaheira's endearing comment: "Khalid my dear, 'twould take a sailor to untie that tongue."