However, I've just looked it up in Merriam Webster, and it looks like this term can include female members, too, even thought the word and the related adjective have strong masculine associations. Wikipedia basically says the same, "Although membership in fraternities was and mostly still is limited to men, ever since the development of orders of Catholic sisters and nuns in the Middle Ages and henceforth, this is not always the case. There are mixed male and female orders, as well as wholly female religious orders and societies, some of which are known as sororities in North America."
We don't even have to argue anyway. From a dictionary:
> [treated as singular or plural] a group of people sharing a common profession or interests: e.g. “members of the hunting fraternity”.
Frankly it’s very easy to google.
The choice of the word "fraternity" by the poster above was deliberate and seems to be being used to imply a more severe exclusion of others.