Get two sims of the opposite gender into a
double bed, then click on one of them to activate them then click on the other sim in bed
and you should see try for baby click that then
afterwards you should hear a lullaby if you can't hear it then have both sims relax on the
bed again have one of them activated click on the other sim and if you don't see try for
baby then congratulations! your female sim is pregnant! And to get dad pregnant have an
adult male sim stargaze at night with the farstar e3 telescope(it's the most expensive
one) sometimes aliens will abduct him he'll come back three hours later but he'll ALWAYS
come back pregnant, whichever
happens everything will seem normal but your pregnant sim might have morning sickness and
throw up in the toilet, while they're doing that they'll have a thought bubble that has a
pacifier and a green question mark, then the next day they'll automatically change into a
maternity outfit and belly will get a little bigger, the next day about the same time as
the first day their belly will get a little more bigger, then the next day their belly
will be HUGE and then a couple hours later they'll go into labor, game will pause for a
few seconds and then ta-daa! you'll have a baby! and then you get to name it. if it's the
alien abduction pregnancy the baby will always
look very alien but they might have their dad's eye color, otherwise their eyes will be
black. (while your sim is pregnant their hunger bladder and energy will decay faster, and
when they start wearing their maternity outfit and get the first baby bump, other sims
can click on the pregnant sim and under baby,they can rub the sims belly or talk to the
baby inside.) (twins occur randomly 10 percent of the time when they do and when the game
is paused while the sim is in labor the baby card will say: there's TWO new babies in the
family! when that happens the first baby is born as described above except when the time
for naming occurs, the first baby gets handed off and the second baby is born without
the birth cinematic, when that's done two naming boxes will come up,allowing you to name
both babies!) If you want to get twins for sure then have the sims 2 open for business
installed then while the sim is in labor bring up the cheat box by typing Shift,Ctrl and
the letter C at the same time. Then type Forcetwins and they'll have twins they'll either
be two boys two girls or one of each (sorry i don't know any cheats to make twins genders
definite or just one baby's gender either.)

I hope this helps!
(Sorry it's so long) ;-)+