Mirror twins share reflection-like traits, from birthmarks to handedness. Here’s what that means – and why it’s more fun fact than medical label.

Around 1 in 250 pregnancies result in identical or “monozygotic” twins, but the mechanism behind monozygotic twinning has remained elusive, partly because the phenomenon is so rare and partly due to ...

Although there are some rare exceptions, identical twins are almost always the same sex. Because identical twins occur when a single fertilized egg splits and forms two embryos, each embryo has the ...

For the best experience, please enable JavaScript in your browser settings. Following the Kakamega twin puzzle that has drawn the attention of the entire country, we ...

You've probably heard of identical and fraternal twins, but a report published Thursday says there's a third kind -- sesquizygous twins or "semi-identical." Identical -- or monozygotic -- twins pop up ...