Understanding Fraternal Twins: Genetics, Appearance & Facts

Twins are undeniably extraordinary; two babies born at the same time, delivered in sync, and brought up together. While most people assume that twins are identical, this is not always the case.

There are two different types of twins: identical twins and fraternal twins. Below we are going to focus on fraternal twins. 

What are fraternal twins? Fraternal twins are two nonidentical siblings born at the same time. Whereas identical twins form from one egg that splits resulting in two babies with the same DNA, fraternal twins result from the mother releasing two eggs during ovulation that are then fertilized by two different sperm cells.

Fraternal twins can be alike or different. They can look very similar or quite different. Their personalities can be polar opposites or one and the same. Each set of fraternal twins is different, just like each non-twin is different.  

Since fraternal twins share the same amount of DNA that any non-twin siblings share, they will be no more genetically alike than singletons.

Understanding Fraternal Twins

Fraternal twins can be just alike or polar opposites. Identical twins are usually two identical people; they share the same DNA, so they are almost just alike.

Fraternal twins, on the other hand, do not share the same DNA, so they can look and act differently.

Fraternal Twins Definition

Fraternal twins are two babies that develop from two separate eggs. They are not always of the same sex or are any more similar than any other types of siblings.

Unlike identical twins, fraternal twins share their own unique DNA and characteristics. Fraternal twins can look alike or be completely different. They can share the same personality or possess different ones.

Fraternal Twins vs. Identical Twins

Fraternal twins result from a mother releasing two eggs during ovulation. Each of these eggs is then fertilized by different sperm, resulting in two siblings born at the same time but with different DNA.

Identical twins come from the same egg that splits for unknown reasons. Fraternal twins are no more alike than any other siblings. Identical twins share the same DNA, making them the closest any two people can be. 

How Are Fraternal Twins Formed?

Fraternal twins are the result of the release of two eggs that are then fertilized by separate sperm. Think of it like having two pregnancies at once.

Women typically only release one egg during ovulation, resulting in one baby, but with fraternal twins, the mother releases two eggs, resulting in two babies. 

Do Fraternal Twins Share a Placenta?

Because fraternal twins are from two separate eggs, each fetus usually develops its own amniotic sac and placenta. Fraternal twins form their own separate structures in the womb.

How Common Are Fraternal Twins?

Fraternal twins are more likely than identical twins. The chance of conceiving fraternal twins is 23 per 1,000 births, so there is about a 3% chance of naturally conceiving fraternal twins.

If fertility treatments are used, there is a 12% chance of conceiving fraternal twins. If the mother is a fraternal twin herself, she has a 1 in 17 chance of conceiving fraternal twins.

How Much DNA Do Fraternal Twins Share?

Fraternal twins share about 50% of each other’s DNA. They do not share any more DNA than other siblings who come from two different pregnancies.

Fraternal twins will share some of the same genes, so they could have a lot of similar features, just like non-twin siblings.

Can Fraternal Twins Be the Same Gender?

Unlike identical twins who are always the same gender, fraternal twins can be the same or different genders. Since fraternal twins come from two separate eggs, they will have their own DNA and be their own unique person. 

Do Fraternal Twins Look Alike?

Fraternal twins will not look exactly alike. They will share the same percentage of DNA as non-twin siblings, so they could look similar or even very close to each other.

Siblings born at different times can look a lot alike or be totally different; it is the same with fraternal twins since they come from two separate eggs. 

Fraternal twin sisters with long blonde hair and matching pink tank tops.

Can Fraternal Twins Be Identical?

There is a minimal chance that fraternal twins will look identical. This can be because they are the same age and are closely related.

Think of having non-twins; looking back at their baby pictures around the same age, they may look very similar, but now that they are older, they may look completely different. In reality, fraternal twins are not identical and have their own unique characteristics.

Fraternal Twin Characteristics

The characteristics of fraternal twins are the same as non-twin siblings. They can have totally different personalities and look completely different.

Even though they are twins, they have their own unique DNA, resulting in them being their own unique person.

Do Fraternal Twins Run in Families?

Since fraternal twins are the result of hyperovulation, they can run in families.

If fraternal twins run on the mother’s side of the family, there is an increased chance of her also having fraternal twins. This is due to genetics passed on to the mother.

If fraternal twins run on the father’s side of the family, it will not make a difference in the chances of him having fraternal twins himself. 

Can Fraternal Twins Have Different Fathers?

Fun fact: Fraternal twins can have different fathers. Since fraternal twins are the result of two eggs being released, they can have two different fathers.

If the mother produces two eggs during ovulation and then has sexual intercourse with more than one man, this could result in each egg being fertilized by a different man’s sperm cells. 

Similarities Between Identical and Fraternal Twins

Fraternal and identical twins can share some similarities. Both fraternal and identical twins have different fingerprints.

Identical twins usually look the exact same, but there is a chance that they may look slightly different, like fraternal twins.

Both types of twins typically share a very close bond that remains strong throughout their lives.  

Fraternal Twin Facts

All twins are interesting. Identical twins might be more interesting since the cause of identical twins is unknown, but fraternal twins are unique too. There are some facts that you might not know about fraternal twins. 

  • Fraternal twins are the most common type of twins.
  • Fraternal twins can have two different fathers and can even be conceived at different times.
  • Fraternal twins can have two different skin tones.
  • After the first twin is born it could be minutes, hours, or even weeks before the next twin is born.
  • Twins can have different birthdays and even be born in different years.
  • If one twin is born prematurely, doctors may be able to stop or delay the delivery of the following twin.
  • If a woman undergoes in vitro fertilization and both eggs are fertilized but one is frozen and then used years later, this would result in fraternal twins being years apart in age.

Related Question:

What Is Twin Telepathy?

Being a twin means you might be able to feel what the other twin feels. Twins sometimes share the same thoughts and dreams! Twins can have the same emotions in a situation and even do the same thing simultaneously.

This is more common in identical twins than fraternal since they share the same DNA, but the phenomenon can occur in both. Twins have been together since day one, so they can develop many of the same characteristics. 

Final Thoughts

Whether identical or fraternal, the idea behind twins is spectacular. Having their own language, being able to feel what the other twin is feeling, and finishing each other’s sentences is just amazing.

Fraternal twins might not be any different than non-twin siblings but they still share a unique bond, and facts about them are all very interesting.