Other Types of Twinning

Polar Body Twins Some research suggests another type of twin called "polar body" or "half-identical" twins. This type of twin is supposed to occur when one egg splits before fertilization and is then fertilized by two separate sperm. It is believed that these twins share 75 percent of their DNA; they share identical DNA from the egg and different DNA from the sperm.

Ever heard of twins who celebrate their birthdays months apart? What about twins who have different biological fathers? This seems impossible, but it turns out that both of these things happen. These incidents are rare, but real.

As we mentioned earlier, some women can release more than one egg during ovulation. In some exceptional instances, these eggs are released at different times. Perhaps at 12 or even 20 days apart. Now, let's say both of these eggs are fertilized shortly after they are released. The woman conceives twins, but on two separate dates. Since the dates of conception differ, so will the dates of delivery. The twins could be born a couple of weeks or a month apart. This is known as superfetation.

When a mother releases more than one egg during ovulation and has intercourse with more than one male during that time, it may result in superfecundation twinning. Two distinct sperm from two separate individuals fertilize the two eggs the woman ovulates. Obviously, the twins resulting from superfecundation are dizygotic.

Now that we know how twins happen and what kinds of twins there are, let's see who is likely to have them.

Well Known Womb Mates Some of these siblings share the limelight, while others reserve their supporting roles strictly for family scenes. Mario and Aldo Andretti Nicholas Brendan and Kelly Donovan Giselle and Patricia Bundchen Jenna and Barbara Bush Aaron and Angel Carter Vin Diesel and Paul Vincent Diedre Hall and Andrea Gengler Jerry and Terry Hall Linda Hamilton and Leslie Hamilton Gearran Evan and Jaron Lowenstein Jill and Jacqueline Hennessy Scarlett and Hunter Johansson Ashton and Michael Kutcher Jason and Jeremy London Evan and Jaron Lowenstein Janel and Carey Maloney Alanis and Wade Morissette Tia and Tamera Mowry Mary-Kate and Ashley Olsen Parker and Chris Posey Marissa and Giovanni Ribisi Isabella and Isotta Ingrid Rossellini Cole and Dylan Sprouse Kiefer William Frederick Dempsey George Rufus Sutherland and Rachel Sutherland