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 ...

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.

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 ...

You can have three babies that are identical (if one egg splits into three embryos), three babies that are fraternal (if three separate eggs are fertilized), or two babies that are identical and one ...

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 ...

Sam and John Fetters are identical twins with autism. But Sam is in college, while John still struggles to form sentences. Their experience may... These identical twins both grew up with autism, but ...