Can Twins Have Different Fathers?

2 years ago3 min read
Last updated: Mar 17 2023

There’s something magical about twins. Whether it’s all the fancy biological stuff that goes on to make it all happen, or the endless possibilities for a childhood of matching outfits and novelty Halloween costumes, we are so here for it. But now we’re asking, can twins have different fathers? It seems so unlikely, and yet, the answer is yes! But only in some very specific circumstances.

Can Twins Have Different Fathers

So, here we are. Answering all your questions on heteropaternal superfecundation. Cool name, huh?!

In this article: 📝

  • Can you have twins to two different dads?
  • What is it called when twins have different fathers?
  • Can a woman get pregnant by two different guys at the same time?
  • Can twins be conceived on different days?
  • What are the heteropaternal superfecundation odds?

Can you have twins to two different dads?

Yes, but only in certain cases. Can identical twins have different dads? No — because identical twins originate from one egg being fertilized by one sperm. But can fraternal twins have different fathers? Yes! These twins develop from two separate eggs being fertilized by two separate sperm, and in some cases those two sperm could be from two different men.

What is it called when twins have different fathers?

The technical name for twins with different dads is heteropaternal superfecundation. Heteropaternal means “different fathers” while superfecundation means the fertilization of a second egg during the same ovulation cycle.

The result is bi-paternal twins — twins with different fathers — who, although born at the same time, to the same mom, would biologically only be half-siblings with 25% of the same genetics. (Full siblings share approximately 50% of their DNA.)

Can a woman get pregnant by two different guys at the same time?

Yes. In the rare occurrence that a woman releases more than one egg in the same cycle, known as hyperovulation, both eggs can be fertilized by different men. Each egg remains viable for 24 hours after ovulation, and sperm can live inside the woman’s body for up to 6 days, so if the woman has intercourse with two different men within that fertile window, it is possible for each egg to be fertilized by a different man.

Heteropaternal superfecundation can also be the result of mistakes made in clinics offering IVF where sperm samples from different men may be cross-contaminated, or mistakenly stored, labeled, or used. Thankfully the chances of this happening are extremely low.

Can twins be conceived on different days?

Yes! Identical twins require one egg to be fertilized by one sperm, so these twins will always be conceived at the same time. However, fraternal twins are the result of two separate eggs becoming fertilized, so they can be conceived on different days.

What are the heteropaternal superfecundation odds?

There’s not much in the way of proven statistics when it comes to quantifying the number of twins born with different dads. One study suggests it could be as high as one in 400 sets of fraternal twins born in the US, but this really is just a guess.

In many cases, the existence of bi-paternal twins only comes to light due to paternity testing through the courts, perhaps as a result of support claims by one parent or custody battles between couples. Because of the stigma attached to women with multiple sexual partners, or the secrecy of extramarital affairs, it’s often an unreported and mostly unknown phenomenon.

So there you have it. Heteropaternal superfecundation isn’t necessarily the catchiest name to trip off your tongue, but now you’ve heard of it, we bet it’s one you won’t forget!

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