So, I'm working on a story, and I have an annoying tendency to drag a boatload of twins into the story. Currently, I have three sets-one set being the main antagonists, another being tragically separated, and the third being among the major protagonists. All three sets are related, with the first two sets being brother/sister (s), and the third set being children of one of the children of the first two. First off, can I seriously pull off the "Twins run in the family" stunt? Second, how common/uncommon are twins? Third, should I use identical twins, unidentical twins, doppelgangers, boy-boy twins, boy-girl twins, or girl-girl twins? Fourth, should I even use twins? Lastly, what are pitfalls I could run into when portraying twins in my writing?