Erudite fluther vocabularians, what is the “sister” equivalent of the word “brethren”?

Sistren.

There is none that I know of. Given my upbringing, I’m pretty sure I’d have heard it if there were one.

Seems that “sistren” is, indeed, the thing! A bit obvious, but I guess it’s legit. Thanks, @gorillapaws!
https://www.merriam-webster.com/dictionary/sistren

I was pulling for Cistern….. that was a deep thought.

@elbanditoroso Well, well, well

<groaning>

The word comes down from a time when women didn’t count, which is clearly reflected in the cults responsible for our memory of it.

Let this be a lesson to not disregard the wisdom of simian scholars.

Sisterhood?

sorority?

Both brethren and sistren were used in Middle English (12th to 15th centuries) simply as the plural forms of brother and sister. From about 1600, brothers began to take over from brethren (Shakespeare used both), except when referring to fellow members of a religious community, or a society or profession.
https://en.oxforddictionaries.com/explore/what-is-the-female-equivalent-of-brethren/