CNN article: http://www.cnn.com/2003/WORLD/europe/10/12/italy.twins.ap/index.html ROME, Italy (AP) -- Four-month-old twins, a boy and a girl, from Greece who were joined at the temple were successfully separated during surgery at a Rome hospital, a hospital official said. Now correct me if I'm wrong here, but conjoined twins result from incomplete cytokinesis in the newly fertilized zygote, a process that if completed leads to identical twins if the two cells separate from each other, right? Therefore, all conjoined twins are identical twins, and must be the same sex. How is it possible that a boy and a girl end up as conjoined twins? Some kind of fusing of fetuses is almost certainly impossible as well, because something only one in 8 million or so fraternal twins share a placenta, and thus amniotic sac. i.e., its extremely rare.