I was trying to translate the name of the game Smash Brothers into Esperanto. The best name I could find is Frakas-Gefratoj, but the ge- prefix feels clunky. I am wondering if I could remove it in order to improve the rhyme. Note that it is obvious from context (the box-art and the game) that it is about gefratoj, and not only about virfratoj.
Given that the original game is named “Smash Brothers” and not “Smash Siblings”, regardless of context, I would say that you could very well remove the ge- prefix.
Pri la ĝenerala demando ĉu oni devas meti la ge- kiam temas pri kaj fratoj kaj fratinoj mi dirus ke jes, oni ja bezonas tion. La vorto frato strikte temas pri viroj, kaj uzi fratoj por priskribi grupon kiu enhavas virinojn similus al nomi ilin viroj - tio certe tre ofende ignorus unu parton de la grupo.
Tamen en ĉi tiu okazo nek la originala titolo havas multe da senco ĉar la roluloj estas nek fratoj nek viroj, do mi rekomendus pli striktan tradukon sen la ge-, kiel rekomendas miestasmia.
Regarding the general question of whether you should put the ge- prefix when it's about both brothers and sisters I would say yes, that is necessary. The word frato is strictly about men, and using fratoj to describe a group of both men and women would be similar to calling them viroj - that would certainly leave out a part of the group in a possibly offensive way.
However in this particular case the original title doesn't make much sense either because the characters are neither brothers nor men, so I would recommend using a more strict translation without the ge-, as recommended by miestasmia.
In fact, the ge- prefix combines the two genders. Gefratoj means that you're talking about brother(s) and sister(s). If there are only brothers or only sisters, you technically can't use this prefix.
Another case: If you talk about your parents, you'll say gepatroj, which means mother and father.
The simple answer to your question is: Yes, the “ge-” prefix in “gefratoj” is necessary. But that is only if you are really translating something like "brothers and sisters" or "siblings". Others have already noted that gefratoj would be simply wrong for brothers.
It seems to me your task is not so much translating anything but creating a suitable, good-sounding Esperanto name for a game called Smash Brothers. Such trademark-like names obey their own translation criteria, and exact word-to-word resemblance is not one of the requirements. But it certainly is not forbidden to be literal, so Frakas-Fratoj is not a bad candidate. You might also try Rompofratoj, Fratoj Kraŝkraŝ, La Frakasuloj, La Rompularo, Bum-bum-kamaradoj... But as I don't really know the game these suggestions may be quite unsuitable.
Well, for translating "brothers" it is not only unnecessary but also plain wrong. The English word "brother" means a male sibling, doesn't it? And "gefratoj" clearly means siblings of both genders.
The words for family and relatives clearly default to male. So if you talk about "miaj fratoj" you clearly mean your (male) brothers. If you have sisters you would exclude them when saying "miaj fratoj".
So if you mean your brothers and sisters you have to say "miaj gefratoj". That's true for all the words for family and relatives like patr-, fil-, onkl-, av-, nep-, nev-, kuz-, edz-.
Maybe one exception: infan-. You don't say "miaj geinfanoj" but only "miaj infanoj" (but "gefiloj")
That said I want to mention that the situation is much more confusing outside the family word field. A good read about that is once more in PMEG.
If you say gefratoj, you are talking of brothers and sisters (siblings).
You can use it, in the same way somebody asking if you have siblings would use gefratoj. If you know there are just brothers, then you should use fratoj, in the same way a person who knows you have brothers would do when asking you how many brothers you have.
Ge- combines genders so gefrato would be 'sibling', gepatro would be 'parent', etc; so if it's supposed to be brothers, ge- shouldn't be used.