When two people form a BrotherBand, they can contact each other at any time. They also learn their friend's secrets, so BrotherBands are only formed between people that really trust each other. BrotherBands can also be formed between planets, such as how Kelvin Stelar attempted to form one between Earth and Planet FM using his satellite.
Forming a BrotherBand grants players with extra Link Power and gives players special benefits such as Brother Cards which can be used in combat. These special cards can act as both the selected Brother's favorite card, or grant the player that Brother's transformation depending on their version of the game that they play.
As revealed in MegaMan Star Force 2, the BrotherBand was created by Lan Hikari as an adult in an attempt to unite people the same way he and MegaMan.EXE were connected.
Geo forms his first BrotherBand with Sonia after releasing her from the control of Lyra. He then becomes Brothers with Luna after releasing her from the control of Ophiuca. Bud becomes his third Brother after saving them from Jammers. Zack becomes Brothers with Geo after he gives him self-confidence by telling him that he helped save Echo Ridge(after the game). At one point, he cuts all his Brotherbands after Omega-Xis leaves him and he becomes depressed and lonely again, but after fighting with him against the FM-ians, he restores his BrotherBands.
In this game, BrotherBands grant special abilities to the player, depending on who they are formed with. For example, forming a Brother with Sonia grants First Barrier and Undershirt, and forming a Brother with a Pegasus player grants a +1 to Custom Gauge speed. Every BrotherBand, however, will always grant a boost to HP.
As the player plays through and completes more of the game, his BrotherBands with NPCs will strengthen and grant a larger HP boost. As real-life Brothers complete more of the game and increase their Levels, their HP bonus and ability granted by their BrotherBand will also strengthen.
In the second game, Geo begins by receiving his new Star Carrier, which forces him to reform all of his old BrotherBands. The Star Carrier also introduces the concept of Link Power, which grows higher with an increase in the number or strength of BrotherBands. The game also introduces a section for real Brothers (which uses the same interface as the first game), and provides an Auto Brother who is from the version of the game not currently being played. During the course of the game, Sonia cuts her BrotherBand with Geo temporarily to convince him and Dr. Vega that she is his enemy, but later restores it after betraying Vega.
Forming BrotherBands in this game will increase a player's Link Power, which in turn can be used to equip several Ability Waves. In-game Brothers can grant you up to 100 Link Power each, while real-life Brothers grant up to 150 Link Power, depending on how much of the game the person has finished. Forming Brothers across different versions are important so as to be able to use the advantages granted by Double Tribes and Tribe King. When a player gains a real-life Brother, he also has the option of forming a BrotherBand with that Brother's in-game Auto Brother.
Geo trades in his Star Carrier for the new Hunter VG, forcing him to once more reform his BrotherBands. Much like the second game, BrotherBands grant boosts to a player's Link Power. This time, however, a player can form BrotherBands with even more in-game NPCs by helping complete sidequests. Real life Brothers grant a player their Brother cards, which allows for the player to Merge Out with their own Noise Change, in addition to the original roulette function. Real-life Brothers now grant up to 130 Link Power.
Also introduced is the Purpose System, a system that functions similarly to BrotherBand. Up to 7 different human players with the same team name will be grouped together, with each player sharing the bonuses granted by their inputted Purpose Card, should they already have finished the main storyline. Also, additional Link Power will be given to a player if a Brother is also part of the team.
BrotherBands aren't shown to be formed by people but there is a large BrotherBand satellite that was used to try and form a BrotherBand with Planet FM. It broadcasted until Cepheus withdrew the FM-ians from Earth. Then it shut down. It is shown that Kelvin created the BrotherBand for the purpose of creating bonds with other people, but in a different way than the games. In the anime, the BrotherBand can eliminate the negative emotions of a being. This could be used on Em beings and possibly humans. By eliminating the negative emotions, the one purified can then begin to understand one another, which would create bonds between anyone. Kelvin used this to purify and form a BrotherBand with Planet FM. However, there seems to be one weakness to this. Apparently, the BrotherBand must be accepted by the target of the wave, otherwise, it won't work. When the BrotherBand was used on Planet FM, it took several months for the BrotherBand wave to be finally accepted.
Kelvin wishes to scour the universe to make even more BrotherBands with other planets. He says until then, Geo must watch over and protect the world.
- The term Brother when referring to BrotherBands is indiscriminate to gender.