Fun Facts about Multiples
please be advised that these facts were gathered from multiple resources and should not be misconstrued as medical opinion or advice.
What is the difference between Identical and Fraternal?
"Are they identical or fraternal?" This is probably the most common question asked of parents of multiples. Many people do not understand what they are really asking, assuming that it is just a matter of twins having similar physical appearance. But twin type is actually determined long before the twins are born. The terms identical and fraternal are common words that refer to zygosity -- the characteristics of the cell union that happened at conception.
Identical (monozygotic) twins result from a single fertilized egg that splits into two, resulting in same sex twins who share 100% of their DNA. There is no genetic marker and no explanation scientifically as to why this happens. No one knows what causes identical twinning. The babies will have identical DNA with the only varying identifiable factor being slightly different fingerprints. Identical twins can actually look very different and are always same-sex sets.
Fraternal (dizygotic) twins are thought to be genetic and this predisposition can cause women to be more likely to release more than one egg at a time, offering the chance for more than one egg to be fertilized at a time. Other factors that can increase your chances of having fraternal twins include using fertility treatments and a mother being over 35-40 years old when she becomes pregnant. These twins share only 50% of their DNA, just like regular siblings, and can be same gender or boy/girl.
How common are twins?
The rate for identical twins/multiples is random and universal; it's the same for all countries and ethnicities and this has remained constant over time. Among general popluations, the chances of having twins in the 21st century are about 3 in 100, or about 3%. Of the identical twins, half are male/male, and half are female/female. If one of your parents is an identical twin or if you (or your partner) is an identical twin, your odds are no higher for having twins than anyone else.
Do twins run in families?
There is no evidence that identical twins run in families. However, fraternal twins do run in families. A woman can inherit the twin gene directly from her mother or from her paternal grandmother through her father. These women may carry a gene for hyperovulation, which means they release more than one egg during an ovulation cycle, increasing their ability to conceive fraternal twins. This is why many people believe that twins sometimes "skip a generation."
Having twins in the family does not make a man more likely to father twins himself, as his genes have absolutely no influence on whether his wife's ovaries will release multiple eggs. However, a man with fraternal twins in his family can pass the twin gene on to his daughter, increasing her likelihood of releasing multiple eggs and conceiving fraternal twins.
"There are two things in life for which we are never truly prepared: twins."
- Josh Billings
Famous Celebrity Twins
Elvis Presley (twin died at birth), Gissele Bundchen, Jill Hennessey, Jose Canseco, Isabella Rosellini, Ann Landers, Mario Andretti, Aaron Carter, Scarlett Johnansson, Kiefer Sutherland, Justin Timberlake (twin died at birth), John Elway, Alanis Morrisette, Vin Diesel, Linda Hamilton, Mary-Kate & Ashley Oslen, and Ashton Kutcher.
Famous Parents of Twins
Patrick Dempsey, Angelina Jolie & Brad Pitt, Julia Roberts, Chuck Norris, Dennis Quaid, Al Pacino, Michael J. Fox, Marcia Cross, George W. Bush, Mel Gibson, Nancy Grace, Ray Romano, Holly Hunter, Jane Seymour, Marc Anthony & Jennifer Lopez, Robert DeNiro, Ricky Martin, and Denzel Washington.
Blow your mind fun facts
Genetically speaking, the children of identical twins are half-siblings rather than cousins. If each member of one set of identical twins marries one member of another set of identical twins then the resulting children would be genetic full siblings.
Fraternal twins can, in some instances, have two fathers. If the mother is, let's say "active", two eggs can be fertilized by two different fathers. Mirror-Image twins may be a partial explanation for the fact that a little over one third of identical twins are left-handed, double the rate in the general population. In extreme cases, all of the internal organs are reversed in one of the twins, with the heart on the right, the liver on the left, and the appendix on the left.
One can also have Half Identical Twins (Polar Body Twinning). These twins occur when the mother's egg splits before fertilization and then each half is then fertilized by a sperm. These twins share 75% of their DNA.