Does anyone know what the term Irish Twins means?

Question

Does anyone know what the term Irish Twins means?

Answer 1

Siblings born less than 12 months apart - usually in the same calendar year, or who are in the same class in school. I think it stems from the perception that Irish people used to have children one after the other, creating huge families.

Answer 2

Siblings born in the same year/less than 12 months apart.

Answer 3

Siblings born in the same year ie a very short gap between pregnancies; common in catholic societies where contraception is frown upon  

Answer 4

Children who are not twins, but close to the same age.  Ireland being a staunch Catholic country, birth control was long taboo, so the Irish gained a reputation for procreation.  Hence, having two children born within the same year led to the reference to the Irish.

I guess it could be construed as a mild slander, but at the same time, if fertility is prized, lose any perjorative connotation.