When two people are born with the same exact energy are born, they're called Energy Parallels. They always have the same element, nature, density, and energy signature, which causes people to sense two of the same. They may, however, have different proficiencies.
Energy parallels can "mix" their own energy with each other's, thus giving them the ability to combine techniques, attacks, and spells. They can also transfer energy to each other easily and without the need of the complicated Energy Transfer technique. They can also sense each other's location, even if they're not sensors, of if they're supressing their energy.
Energy parallels always get along extremely well, and understand each other better than anyone else. Same-gender parallels usually end up becoming best friends for life, and opposite-gender parallels usually end up married.