• 18% to 22% of twins are left-handed compared with under 10% for non-twins.
• The incidence of fraternal twins varies by race:
  Of African descent: 1 birth per 70
  Of Caucasian descent: 1 birth per 88
  Of Japanese descent: 1 birth per 150
  Of Chinese descent: 1 birth per 300
• Genetic factors do not appear to have much affect upon the incidence of identical twins.
• Identical twins exhibit almost identical brain wave patterns.
• William Shakespeare was the father of boy/girl twins Hamnet and Judith. He also wrote about twins in The Comedy of Errors and The Twelfth Night.
• The term "twins" derives from the ancient German word twin or twine meaning "two together."
• Twinning does run in families, but supposedly only fraternal twins and not identical twins. Yet there are many, many families with identical twins in each generation, and sometimes even several sets of identical twin children, so this ostensible scientific "fact" doesn't seem to be supported by the evidence. There is little evidence to support the popular notion that twins "skip" a generation.
• If the mother is herself a fraternal twin, the chances of having twins increases about five-fold.
• The modern world record for giving birth to multiples is held by Leontina Albina from Chile, whose 55 children included three sets of triplets. The all-time historical record is claimed by a Russian who is purported to have given birth to 6 pairs of twins, 6 sets of triplets, and 4 sets of quads. (If true, it means her 46 children included no singletons at all!)
• The scientific study of twins is known as "gemellology."
• Twins have been known to develop their own "language" that only they understand. This process is known as "cryptophasia."
• The average time between the delivery of the 1st and 2nd twin is 17 minutes.
• Multiples usually arrive a bit early and are born at 28 to 35 weeks of gestation (the average non-twin is born at 37 weeks).
• If identical twin sisters or identical twin brothers bear children, the children are genetically half-siblings. It's as if the woman had children with 2 separate men or if the man had chilren with 2 different women. If idential twin women marry identical twin men and both couples have children, the children are genetic siblings, but legally they are first cousins.
  
  Prenatal characteristics
  Twins that get to 34 weeks in the womb are considered term. As would be expected, the average weight at birth for twins is lower than the normal weight of singletons. (2,376 grams vs. 3,351 grams).
  
  Labor and delivery
  In the majority of twin pregnancies, labor begins between 28 and 33 weeks. Techniques available to modern physicians have reduced many of the risks associated with multiple deliveries. The interim between delivery of the first baby and the second baby averages 17 minutes, but the duration can be shorter or as long as several hours or even days. The presence of two babies in the womb can lead to one or both being in a transverse or breech position. Deliveries by cesarean section (C-section) are more common with multiple pregnancies. Sometimes the first baby is delivered vaginally, and the second baby is delivered by C-section.
  
  Nursing and bottle feeding
  Because breast milk provides the most complete nourishment for newborns, many mothers of twins choose to breastfeed. Although many moms worry there won't be enough milk for two, this is generally not a problem. Frequent nursing stimulates milk production. During the first month, infants nurse 7 to 10 times a day. Smaller babies, which twins often are, usually need to nurse more frequently. Twins are often nursed simultaneously, but there's certainly no guarantee the twins will want to nurse at the same time. Mothers elect or switch to bottle feeding for a number of reasons, especially if the breastfeeding schedule becomes exhausting. Even bottle feeding can be a challenge when both babies want to be fed at the same time. A number of inventive techniques (and special gadgets) have been developed to hold all the bottles and babies involved!
  
  The twin bond
  

As any parent of twins will you tell and researchers have documented, twins bond with each other in special ways. This is especially true of identical twins who, after all, share the same genes.

The special bond between twins often shows up in infancy. Baby twins may exhibit similar eating, sleeping, and behavior habits. They may tend to sleep at the same time and, unfortunately, awake and cry at the same time. Some parents note that their infant twins seem to entertain each other while in their cribs. Conversely, when separated some twins become easily upset.

As twins become older, the special bond between them remains even as differences begin to emerge. Playing together is a key part of this bonding. Sometimes, twins develop their own unique language, with words and phrases that are only understandable to them. This is known as cryptophasia. Even in normal conversations, one twin may finish the sentence started by the other.

Because of the special relationship between twins, parents struggle with whether to separate twins into different classrooms when they begin school. While many schools recommend separation so that each child can develop a stronger sense of autonomy, most experts (and parents) believe each situation should be decided individually.

Even as twins mature and develop more independent lives, the twin bond can remain very strong. Adult twins often maintain regular, even daily, contact with each other. Interestingly, studies have revealed that twins reared apart, especially identical twins, exhibit very similar behavioral characteristics even after they become adults. Similarities between twins reared apart show up in their voices, gestures, fears and phobias, and a host of other characteristics.