From MangaHelpers:
Brothers is the name of a trio who use their incredible gifts to accomplish seemingly impossible missions. Not part of any government organization, they work privately for large sums of money. Their leader is Macky Pluto Kara who has a brilliant mind. The other two are HEM, Homo Electric Mechanics, which means that although they are alive, their cells are made of silicone instead of proteins which all humans are made of. It makes them nearly invincible and allows them to have superhuman powers. Rickey Neptune Kara is his older brother and Memory is his younger sister and lover. The Brothers are untouchable, even by the CIA, and carry out difficult tasks for their own benefit.