two sets of twins

記事のタイトルにつられてアクセスしました。


Florida mom gives birth to 2 sets of twins in 1 year

A Florida mom who gave birth to twins twice in one year said she didn’t even know multiples ran in her family until after she welcomed her four boys in 2019. Alexzandria Wolliston first welcomed Mark and Malakhi in March, she told WPTV.com, and then unexpectedly found out in May that two more were on the way, with all four conceived naturally.

“I’m like, ‘Oh my gosh, I never thought I would have two,’” Wolliston, who also has a toddler daughter, told the news outlet.
(Alexandria Hein. Florida mom gives birth to 2 sets of twins in 1 year. Fox News. January 8, 2019.)


何につられたかというと、


2 sets of twins


という部分です。

双子の出産自体珍しいと思いますが、2組の双子を（1年以内に）出産というのは確かにニュースになる話題です。

ところで、英語の表現として、"2 sets of twins"というのはどうなんだろうか、という疑問が湧いたというのが正直なところです。

まず思ったのが、"2 pairs of twins"という表現の方が適正なんじゃないか、ということです。

"set of~"は感覚的にモノ（things）に対して用いられるというように理解しているからですが、Fox Newsの記事のタイトルで使われているくらいですから、誤用の可能性は低いと思われました。

果たして、コーパスで検索してみたところ、"sets of twins"も"pairs of twins"も、両方の用例が存在し、しかも、"sets of ~"の方が用例数として多い（！）ということが分かったのです。


It was a record-setting day at a Long Island Hospital this week -- four sets of twins were delivered there in fewer than six hours! Two of the births at NYU Winthrop Hospital in Mineola on Wednesday were expected, and the other two were surprises, said Dr. Martin Chavez, the hospital's chief of maternal fetal medicine, told Newsday. Even two sets of twins in a single day is rare at the hospital, and four is unheard of, he said.
(New York Post, 2017)


"pairs of ~"の方の用例は下記のようなものがあります。


Harden and three colleagues, including her adviser, Eric Turkheimer, an expert in behavioral genetics, studied more than 500 pairs of twins in the same national survey analyzed by the Ohio team. Because twin pairs share similar or identical genetic inheritances (depending on whether they are fraternal or identical) and the same home environment, twin studies are useful for seeing through false cause-and-effect relationships.
(Washington Post, 2007)


何でもないようなことですが、調べてみると色々面白いですね。