Fraternal twins with different fathers

Heteropaternal superfecundation can occur if a woman releases two eggs in one ovulation period and they are fertilized by sperm from two different men. It can also happen if she ovulates twice within a short period of time.

Fraternal twins with different fathers – statistics

There are less than 10 known cases of twins with different fathers in the world. Experts believe that there are more cases of heteropaternal superfecundation than what’s known. Some families are not aware of the fact that there are twins with different fathers in their family and some choose not to act upon their suspicion. The phenomenon has also become more common with the spread of assistive reproductive technologies, said Jennifer Wu, an obstetrician-gynecologist at Lenox Hill Hospital in Manhattan, to the New York Times. This is because men in gay couples sometimes both contribute sperm to a pregnancy. Twins with different fathers share approximately 25 percent of DNA. Genetically, they are half-siblings.

Recent cases of fraternal twins with different fathers

• A Vietnamese family discovered in 2016 that their fraternal twins are twins with different fathers. This was reported by BBC News in March 2016. The twins had gone through a DNA-test, as relatives pointed out that the 2-year old twins looked remarkably different, and that one of them looked like neither of the parents. A DNA-test ruled out a possible hospital mix-up as both the children were offspring of their mother.

• One case of heteropaternal superfecundation in the U.S. was detected through paternity testing for child support. This occurred in 2015 in New Jersey. An alleged father was being sued for child support. He had to go through a paternity test. The test established that he was the father of one twin and not the other. The court ruled that he only had to pay child support for the child he had fathered.

• The Maury Show have had two different twin moms come on who’ve experienced heteropaternal superfecundation. They got the paternity test results during the shows.

Semi-identical twins with different fathers

Semi-identical twins are called sesquizygotic and develop from the same egg. It can happen when a woman ovulates and releases one egg. That egg is entered by two sperm cells from two different men. The egg is fertilized by both. The fertilized egg now has three sets of chromosomes (as oppose to the usual two) and they split into two separate cell sets. Some of the cells contain the chromosomes from the first sperm while the remaining cells contain chromosomes from the second sperm, resulting in the twins sharing only a proportion rather than 100 percent of the same DNA from the fathers.

How much DNA do semi-identical twins have in common?

The twins can have anywhere from 50 to 100 percent of their DNA in common. They share the same genetic material from their mother and only a proportion of DNA from the fathers.

Semi-identical twins statistics

Semi-identical twins are extremely rare. Only two cases have been reported so far. A set of twins from the U.S. was reported in 2007 and a case of 4-year old boy-girl twins in Australia was reported in 2019. In the last case the twins shared a placenta during pregnancy. They were identical on their mother’s side and shared 78 percent of DNA on their father’s side.

Explains myth

A female fraternal twin has a higher probability of having fraternal twins compared to a woman who’s not a fraternal twin. This is because some women have a hereditary tendency to release more than one egg during ovulation enabling fraternal twins to form. They can pass this tendency on to their daughters. A father who’s a fraternal twin can pass the gene on to his daughters. This may explain why some people mistakenly believe that twins skip a generation.

Increase your chances

There are other factors that predispose you for having fraternal twins. Being tall and overweight seems to increase the chances. Age is also an important factor. Women in their mid- to late thirties are more likely to release more than one egg per menstrual cycle, which means that getting pregnant several times in your late thirties will increase the odds of having fraternal twins. Read more about increasing the likelihood of having twins.

Can twins have twins? We hope we’ve answered your question sufficiently. If you’d like to know more regarding this, then leave a reply below this article and we’ll do our utmost to answer your questions. Also, we would like to get in touch with people, who are twins, and who’ve had twins themselves. Please contact us by writing an e-mail to kate@about-twins.com. 

Identical twins

This type of twin is formed from one fertilized egg being split in two. The eggs develop into two individual embryos that share almost the same genetic material. When developing in the womb, identical twins can share or have their own individual placentas. The same goes with membranes. This sometimes makes it tricky to determine whether or not twin babies are identical or fraternal. Read more about how identical twins are formed to learn how to distinguish identical and fraternal twins from each other, or use our free Twin Test.

Fraternal twins

This type of twin is formed from two eggs being fertilized by two different sperm cells. Fraternal twins are genetically speaking like siblings. They may feel a bit closer, though, as they share a womb and are born at about the same time. As with identical twins there are some patterns of fraternal twinning that are exceedingly rare – read about the different types of twins.

How are twins formed? We hope we’ve answered your questions. Otherwise post a reply below this article and we’ll do our best to assist you. 

One way to tell the difference is using a twin zygosity test, due to the fact that identical twins share almost identical genetic information, while fraternal twins share around half. The twin test is done by swabbing to gently remove cheek (buccal) cells and can be done from home. The procedure is noninvasive and works on twins of any age, newborns to adults. A twin test can be ordered online and is being offered by numerous private companies. However, if you are not up for paying for a DNA-test, you may find your answer by reading the below.

Answer these twin test questions

• Do you have a boy and a girl? Then they are fraternal (but read this).

• Do they have the same sex, AND do you know for sure that they shared a placenta? Then they are identical.

• Do they have the same sex and individual placentas, or is there doubt whether the placentas have fused together? Then they can be either fraternal or identical. In this situation, choosing to be patient may do the trick. According to the Danish Twin Registry you should wait until the newborns are a bit older. If they look so much alike that friends and family can’t tell them apart, they’re likely to be identical. This method works in more than 95 percent of cases, they write on their website.

Consider having (some of ) your children in your thirties

Researchers agree that women in their mid to late thirties are more likely to prepare more than one egg per menstrual cycle than women in their twenties. If two eggs are released the possibility for fraternal twins are present. Getting pregnant several times when you are over the age of 35 will increase your chances of having twins significantly.

Start trying after you stop taking the pill

You need to try conceiving right after you stop taking the pill. This theory based on a 1977 study published in the New England Journal of Medicine suggests that when women first stop taking the pill, their bodies work to re-regulate their hormones. During the first months after getting off the pill, two eggs are sometimes released enabling them to get pregnant with twins. Be aware that other research show, that there is no correlation between ceasing to use oral contraceptives and having twins.

Eat dairy products

Gary Steinman of the Long Island Jewish Medical Center conducted a study that suggests that in particular dairy foods, could boost the production of a protein called insulin-like growth factor (IGF) in women. This could promote the release of eggs by the ovary, so that two are more likely to be released. This is especially the case in areas where growth hormone is given to cattle. Listen to Gary Steinman’s explanation in this video.

Use folic acid as a supplement

Many women take folic acid as a supplement when they’re pregnant. Most do this to reduce the risk of neural tube defects. Some researchers claim that this supplement is also likely to increase the chances of getting pregnant with fraternal twins. This is described in an abstract by Bengt Källén from the University of Lund in Sweden. However, other researchers claim that there is no correlation between the consumption of folic acid and twinning rates. Keep taking the supplement though – it is proven to reduce the risk of neural tube defects.

Be aware of weight

Several studies have showed a correlation between maternal weight and the chances for a twin pregnancy. You have a significantly higher chance of getting pregnant with fraternal twins if you have a BMI over 30. However, obese women are encouraged to lose weight before getting pregnant, as maternal overweight is linked to lower fertility and also increases the risk of babies born with birth defects. The odds of having identical twins do not seem to be related to BMI.

Eat lots of yams

No direct correlation between eating yams and getting pregnant with twins have been proved, but research has suggested that a high occurrence of multiple births could be related to the eating habits of women in specific regions – for instance in a Nigerian town nicknamed Twin Capital of the World – where the intake of yams is known to be high. Read more here.

We hope you’ve learned a bit more about how to have twins. Leave a reply below this article if you have any tips or tricks on how to have twins.