Find out everything you've always wanted to know about identical twins – from how they form to what makes them unique.

Even fewer cases of semi-identical (sesquizygotic) twins have been reported in medical literature. In these cases, a single egg is fertilized by two sperm. The egg then divides and develops into ...

It is the first time semi-identical twins have been identified during pregnancy. The first-time mother was 28 at the time and had conceived naturally, doctors said. The case is being reported on ...

Photographs showed the facial differences between twins, one of whom allegedly smoked and tanned for 16 years while the other ...