Twins is actually a random happening in the game, much like alien abductions and death by flies. There is the rumor of the "cookie diet" that is supposed to casue twins. Players force their newly-pregnant sims to eat nothing but cookies until day two of the pregnancy. I tried it a couple of times, and it did work once. But, not sure if it was actually a coincedince or what. The easiest way is hacks and mods. Look around the two really good mods sites, www.modthesims2.com and www.varioussimmers.com for those sorts of hacks. I had one called the "Inteenimator" from MTS2 that allowed me to impregnate any sim with my choice with either a single birth or twins. But, I am not sure how compatable it is with other mods. I have heard of problems with its predecessor, the insiminator, and UNI. As for girls: I've always heard to save right before Mom goes into labor (Like before she goes to sleep when you know she's going to have the baby in the middle of the night), and then if you get a boy baby, exit without saving. Sometimes you have to do that a number of times, though, because the game will try to keep a balance in the number of male and female sims in your neighborhood.
