Actually I do have nieces who are identical twins, and I do have a hard time to call their names because they are really look-alike. Then the question is why some twins are look-alike, and some are not. Here is what I have learned through my online reading.

When a couple have an intercourse, the woman could have her egg fertilized by a sperm from her partner. Normally the fertilized egg will produce one embryo, resulting to one baby. That is a normal fertilization from one egg & one sperm, and the result is one baby at the end. For twins, it is different and there are two abnormal scenarios:

1. The woman egg is fertilized by one sperm as normal, but for some reason, the fertilized egg divides into 2 embryos, resulting to 2 babies. We call them identical twins. They look alike and we hardly differentiate them. They will have the same genetic identification (DNA). They both have the same sex (either male or female).

2. For some reason the woman has 2 different eggs in the first place, and the two eggs will be fertilized by 2 distinct sperms. The result is two different embryos, resulting to 2 babies. We call them fraternal twins. They do not look alike, and their genetic identifications are different. That does make sense because they come from 2 different eggs and sperms. They just like normal siblings. This case is what happens to a couple who lives in England. They have 2 set of twins, and both sets have one dark and one light skins. They were on the USA national news a couple weeks ago.

Many or all of us may have seen some weird twins on the news or magazines. They share live together because their body parts fused together. They are called “conjoined twins”or “Siamese twins”. Some have one body, one head, but two faces. Some have back-to back fused together. Actually there are various types of conjoined twins. They are actually identical twins. The question is why they have joint parts. The answer is because the splitting into 2 embryos stops before the process of splitting (division) completes. If the split process complete, there would be two healthy normal identical twins.

Many of us may have seen President Bush twins daughters on the news or Magazines. Can you guess if they are identical or fraternal twins?

Many of us may have seen triplets, quadruplets, quintuplets, or sextuplets on the news or Magazines. Can you guess if they are identical or fraternal?