A. Phex Brothers

Although both brothers are identical in appearance and attire, they have small differences to distinguish one another. Besides the elder brother's damaged right arm that has Schott Key No.1, the elder brother has his ear piercing on his left ear whereas the younger brother has his on his right ear. Sporting nearly shaven heads with intricate sideburn designs and neck-length ponytails, they wear long-sleeved decorated shirts and shorts which are reminiscent of typical footballer clothing, the latter of which were first shown to have a serrated bottom. Their eyes are squinted to the point of appearing shut a majority of the time.↗

The pair share a duality described as harmonious with one another, being based on the Japanese concept of 'A-un', which explains the connected nature of opposites and their seemingly contradictory similarities.↗

Aside from that, the elder of the two brothers seems to be the one in charge, and was the only one to speak at first, but the younger brother speaks as well later on. The elder brother is the one who communicates with the policemen in place of his brother and the one who displays a Stand power; his brother however would later reveal he also possessed a Stand - hidden in his soccer ball bag. The younger brother is more reserved, preferring to let his older brother do most of the talking. The younger brother also has a habit of kicking around his Stand's container and performing tricks with it, not unlike, and in the guise of, a soccer player.↗↗↗

As twins, the A. Phex Brothers get along well and the older brother even protects and supports his brother, saying that it is not his fault that he attracted attention by playing with the ball. The two have also developed good teamwork in combat, using their abilities in unison to take their enemies by surprise.↗↗

Schott Key No.1

The Stand of the elder brother, Schott Key No. 1, can shift objects touched with his left hand to the stub on his right. He can manipulate the way it materializes for a variety of strategic advantages. The first example of this is shown during the confrontation between the brothers and a pair of police officers who attempt to ascertain the identity of the brothers. Objects transported in this fashion will seem to break down and crumble while the material reassembles on the other end.↗

Schott Key No.2

The younger brother's Stand, Schott Key No. 2, possesses the ability to release potentially fatal toxic gas whenever the Stand's container is opened. Its effect induces a bloody cough when inhaled, and quickly corrodes skin that comes in contact with it. The gas can be transported by Schott Key No. 1 to give the elder brother a deadly technique in combat.↗

Rock Physiology

While similar to a human's, their bodies can presumably change into rock. Because of this, they do not need to sleep or rest. They can mimic rocks to the point that it makes them indistinguishable from them.↗

Norisuke theorizes that Yotsuyu 's physiology requires him to have at least a small amount of skin respiration and in the absence of such his body structure will begin to break down due to it becoming less structurally stable than an ordinary human's. This could be a trait shared by other Rock humans, including the A. Phex Brothers.↗

Miscellaneous

The younger brother demonstrates versatile and dynamic control of his soccer ball common of experts, capable of moving it between his legs and head effortlessly and kicking it with enough force and power that it could be considered an attack of its own.↗↗