I always assumed my brother and I were identical twins. Now my mother, in her eighties, says we are cisternal twins, but I cannot find any references on the matter. Is there such a thing? If so, what traits make them so?

appended: also, we've been called mirror twins. In a study by a student, we learned that our fingerprints are nearly exact opposites.

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    $\begingroup$ Most likely she means fraternal, or dizygotic twins. betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/… $\endgroup$
    – Luigi
    Nov 12, 2014 at 21:00
  • $\begingroup$ that's not it; ty for the guess but I'd like something more definitive. I explicitly mean "Cisternal". I know what fraternal means. $\endgroup$
    – Riverborne
    Nov 13, 2014 at 13:55

1 Answer 1


Cisternal doesn't make sense in this context, so either your mother is using an obscure term (quite possible, these things change a lot) or just has the wrong word.

However, mirror twins are a known thing (and quite cool): http://www.twinsuk.co.uk/twinstips/4/140/twin-pregnancy--multiple-births/types-of-twins--identical-fraternal--unusual-twinning/.

She may have meant something like "chiral twins" or "cis-trans twins", which would be borrowing from a similar concept in chemistry to describe your mirror-image nature (but is, again, not a phrase I've heard in the twin literature.)


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