“The Brothers X” was made popular mostly through business and entertainment acts. Because it originates in a time of male-run family businesses, that’s the reason it’s mostly a male name. “Smith and Sons” implies the father and his two sons working the business. If the father dies “The Brothers Smith” makes more sense, unless possibly the sons have sons of their own and choose to keep the name. Of course, sometimes “The Brothers Smith” would just be two brothers in a partnership together with no father ever involved. Family businesses were so common in part because corporate structures were often not an option available to ordinary folk. Furthermore, many historical (and some modern) laws required the names of the owners to be listed in the name of the business.
Back in those days, women rarely worked, and they rarely owned property. So you wouldn’t expect to see “Smith and Daughter” because in that time your first thought would have been “Why isn’t she married?” (I’m reminded of the Progressive Insurance commercial making fun of the 1950’s, including the line “Where is your husband?”)
Likewise, “Sisters Smith” wouldn’t have made sense - if they got married, neither one would be a Smith any more, and society would have expected them to be both be taking care of the home, not the shop. At many times and places, the two sisters couldn’t even have owned the business themselves without a male figurehead. It wasn’t so long ago that even school teachers, maids and cooks were required to be unmarried. A married woman should be tending her home, not out working.
Nowadays, “The Brothers x” survives as a colloquial phrase and we don’t really think of the origins or meanings. We’re just imitating history. There was no regular usage of “The Sisters X” for us to imitate, so we don’t.