Twin Age: Determining Who Is Older, Should You Tell Them, and More

People love to ask which twin is older when they realize you have multiples. Even if they are only born minutes apart, there is always an interest in who is older.

Which twin is older? The oldest twin is the one who is born first. It doesn’t matter whether twins are born vaginally or by C-section; the first one out of the womb is considered the oldest. This may be the baby who was labeled baby A during the ultrasounds, but it might not if the other one makes it out first.

Birth order can be tricky with singleton siblings, but things can get more complicated with twins. It’s important to know when birth order matters and when it doesn’t. 

A variety of factors can affect who comes out first and when.

Birth Order in Twins

There is a lot of focus on birth order with most siblings, so how does this affect twins? There’s quite a bit to know when it comes to their unique circumstances. Some of the information may be surprising.

Which Twin Is Considered Older

The oldest twin is the one who makes it out of the womb first. That one technically entered the world earlier than their sibling, so they are the oldest. They may be older by seconds, minutes, hours, or days.

What Determines Twin Birth Order

Twin birth order is usually determined by placement in the womb. The twin lowest in the uterus is closest to the exit if a vaginal delivery occurs. This twin would be the oldest because he would come out first. 

In the case of a C-section, doctors try to grab the baby who has been labeled baby A during the pregnancy. However, that’s not always what happens.

During a C-section, it may be necessary to take the baby who is having health issues before their sibling regardless of position. 

Should You Tell Twins Who Is Older?

Every parent has to decide whether it’s a good idea to tell their twins who was born first. If you do choose to tell your children who is the oldest, make sure you don’t overemphasize the significance.

Knowing who is older shouldn’t make your twins feel like one is better and one is second best.

Does Birth Order Affect Twins?

It’s hard to say how much birth order affects twins. Twins may reverse roles with one being dominant at one point in life and the other being dominant at another part.

Twins may also adopt the role they feel they have been given by parents who put a strong emphasis on birth order. 

If a parent treats the older twin like the more responsible child and the younger one like the baby, they may fall into these roles because of expectations, not birth order.

Twins can be affected by overall birth order in the family.

Twins born to a family that already has older kids will likely take on some of the typical youngest-child qualities. Twins who are the oldest in the family may take on more control of their younger siblings.

Does Birth Order Affect Personality?

For twins, it’s unlikely that birth order will affect their personalities. Even for non-twin siblings, questions are being asked about how much impact birth order really has on personality.

Many recent studies are finding that it isn’t as major of a factor as once believed.

Baby twin boys smiling while lying on their tummies.

Is the First-Born Twin Stronger?

Which twin will be stronger depends on a variety of factors. While some evidence does show that first-born twins have a higher body mass index, or BMI, this isn’t always true. 

Are First-Born Twins Smarter?

Studies on twin birth order are rare, and there isn’t anything to show that first-born twins are smarter. 

Are Fraternal Twins Conceived at the Same Time?

For the most part, fraternal twins are conceived at the same time. Two eggs are released, and they are fertilized by sperm close to the same time.

However, since fraternal twins come from two separate eggs, this isn’t always the case.

With fraternal twins, either two eggs are released at the same time or one egg is released and then another follows later. In the latter case, those eggs can be fertilized weeks apart.

Twins With Different Gestational Ages

Though it’s extremely rare, superfetation can cause fraternal twins to have different gestational ages. This rare phenomenon can occur when one egg is fertilized and then another egg is released in the same cycle and fertilized.

The first egg will already be embedded in the uterine wall before the second egg, and this means twins can be days or even weeks apart in gestational age.

Longest Time Between Twins Birth

The longest time between twins being born has been recorded at 90 days. In 1996, Molly West was born on January 1st.

She was three months premature, and since that is not ideal, doctors tried to stop the contractions so her twin brother could stay in longer. It worked, and Benjamin West was not born until March 30th.

Related Questions: 

Does Implantation Happen Twice With Twins?

Both twins implant at around the same time. In rare cases, due to unique circumstances, fraternal twins will not be implanted at the same time.

Can Twins Have Different Birthdays?

Twins can have different birthdays. One twin may be born late at night while the other stays in until after midnight and is born the next day.

If one twin is premature, the doctors might try to stop labor so the other twin can stay in longer. This could result in birthdays separated by days, weeks, or months.

Is One Twin Always Dominant?

One twin is not always dominant. However, one may be more physically or psychologically dominant.

It’s also possible for twins to trade dominance with one being more dominant at certain times and then the dominance switching to the other twin.

Final Thoughts

When it’s time to decide if you want to tell your twins who’s older, make sure you have all the necessary facts about birth order.