To increase your chance of having twins you can have your doctor prescribe you fertility meds. Although most docs wont unless there is a reason to. I am currently on the fertility meds called Clomid. It is supposed to help ovulation and also increases the chances of having multiple eggs released. Another way you could go is IFV. This procedure is very expensive and most insurance companies do not cover it. But if you have the money you can select how many eggs and even a gender - if it works. Some people have to have many treatments to finally fall pregnant. I have also heard of woman eating a specific kind of Yams during ovulation can increase the chance of having twins. Good luck!!