What Does the Term Irish Twins Mean?

What Are Irish Twins?

Irish twins. Credit: Mike Kemp Creative #: 649663241

Have you heard of the term "Irish twins"? It's a somewhat outdated (and considered by many unflattering or derogatory) term used to describe two children born to the same mother in the same calendar year or within twelve months of each other. Irish twins are not technically twins, meaning two people born from the same gestational period, but rather it's a colloquial way to classify siblings that are born in close proximity.


If you use a dictionary to define a twin, you’ll find two types of descriptions. The first is quite literal: “either of two children brought forth at a birth” (Dictionary.com) or “either one of two babies that are born at the same time to the same mother” (Merriam-Webster). 

By that definition, Irish twins are not twins. Twins are two children born from the same conception, carried during the same pregnancy, and born together. 

But because of reproductive and medical technology, one can put forth examples of all kinds of exceptions that violate that definition but produce individuals that would still be considered twins.

(Of course, the phrase Irish twins can also be used to refer to twins from Ireland)

Sometimes the use of the term Irish twins is expanded to describe any siblings that are close in age. Some even stretch the definition to include siblings less than two years apart. (Some would call that "almost Irish Twins" or "practically Irish twins".)

Origin of the Phrase Irish Twins

The phrase originated as a derogatory term associated with Irish immigration to the United States and England in the 1800's. The implication was that large groups of close-in-age siblings were the result of uneducated, poor Irish Catholic families' lack of birth control as well as self-control.


In modern use, the term is not intended as an insult, but rather as classifying siblings born close together. While Irish twins are not actually twins and they are not the same as having twins, many families proudly claim the term to describe the short time span between the births of their children. 

Do Irish Twins Have the Same Birthday? 

Irish twins can conceivably have the same birthday if they are born exactly one year apart, for example on July 31, 2000, and July 31, 2001. 

Can Irish Twins Be in the Same Grade? 

Some Irish twins are in the same grade, depending on when their birthdays fall and school system requirements. For school systems with a late deadline, such as December 1st, it is conceivable that Irish twins could be in the same grade at school. 

Examples of Irish Twins

Here is an example of Irish twins. A mother gives birth to one baby in January of 2007 and another child in December of the same year. Or, alternatively, a mother births a child in August of 2007, becomes pregnant again in October and gives birth to another child in July of 2008.

Are Irish Twins Born in the Same Year?

The term Irish twins isn't precisely defined. While it can describe two children born in the same calendar year, for example, January 5, 2004, and November 29, 2004, it can also be accurately used when two siblings are born less than twelve months apart.

In that case, they would be born in different calendar years but still meet the criteria to be considered Irish twins.

Also Known As: Irish triplets when three children are born to the same mother within three years.

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