10, Identical twins can be of different sexes. It might sound strange to stay that identical twins can be different when it comes to gender, but technically speaking it is possible. It happens when the egg splitting process doesn’t happen quite as it should, resulting in twins that display genetic abnormalities like Klinefelter’s syndrome. This means one twin might have the right correlation of XX or XY while the other has XXY.
11, Twins share DNA, but it is not identical. While identical twins come from the same sperm and egg, their DNA isn’t necessarily identical, according to new research. Scientists used to think differences in twins were due to environmental factors; they now know that isn’t the only force causing variations. Genetic studies have demonstrated that there are certain points where twins will veer away from one another, with one carrying different or multiple copies of the same gene.