Sandbox / Shared Signature Attack

One of them will teach this yet another person eventually.

A technique amongst members of a similar group, family, school of fighting, etc. Characters who share signature attacks often have pre-established lore with each other; it could be a family member inheriting the technique from the other, it could practitioners of the same martial art learning the move, or they perhaps were inspired seeing another character performing it and decided to create their own unique version.

The Hero will often learn their Signature Attack from a teacher or family member, and perhaps put their own twist on the move that expands on it or differentiates it from its predecessors.

Common amongst Moveset Clones, who often have lore ties to their character of origin. Characters who experience Divergent Character Evolution can retain similar attacks while gaining their own unique techniques, further enforcing this trope.

A Sub-Trope of Signature Attack

Compare Moveset Clone.

Examples

Anime & Manga

• Demon Slayer: Kimetsu no Yaiba: The Hero Tanjiro's signature "Water Breathing Style", a style of sword-fighting that mimics the flow and adaptability of rushing water, is actually one he shares with several other demon slayers who learned it from the same master. Giyu Tomioka, one of the nine Hashira, also learned the style and is even more experienced than Tanjiro with it.
• Dragon Ball: The Kamehameha is a technique taught to students of the Turtle School, but ultimately evolved to be the Signature Attack of The Hero Son Goku. It was first invented by Goku's teacher, Master Roshi, and taught to Goku alongside his friends, Krillin and Yamcha. Goku's sons, Gohan and Goten, would later learn to use it too, as have two of Goku's nemeses Cell and Majin Buu who copied it for their own use.
• Naruto: The Rasengan has famously been Naruto's signature technique; a swirling ball of pure chakra that can land a devastating blast on whatever its aimed at. He also has other variations like "Rasenshuriken", a projectile variant, and "Big-Ball Rasengan", an even bigger and stronger ball of chakra. Unbeknownst to him at first though, this technique was actually invented by his, father Minato, who would then teach it to his master, Jiraiya, and his student/Naruto's teacher, Kakashi. Naruto's close friend ,Konohamaru later copied it after seeing it used multiple times, and then years later he'd teach it to Naruto's son, Boruto, who would iterate on it by turning the base Rasengan into a, improvised projectile.

Video Games

• Final Fantasy XIV: The dragon Midgardsormr and his direct children the First Brood can all cast the spell Akh Morn, a Pillar of Light that bombards the target as a Spam Attack.
• Garou: Mark of the Wolves: Rock Howard is the son of series Big Bad Geese Howard, who was then adopted by The Hero Terry Bogard. He thus incorporates many of the two's Signature Attacks into his own repertoire. From Geese he can perform the "Reppuken"/"Double Reppuken", "Rashomon", "Deadly Rave", and "Raging Storm". From Terry he learned how to perform "Rising Tackle", "Crack Shoot", and variations of "Burn Knuckle" and "Power Dunk" called "Hard Edge" and "Rage Run - Type Dunk" respectively.
• League of Legends: Brothers Yasuo and Yone were both trained in the powerful "Wind Technique", allowing them to harness the power of the winds through sword fighting. This is reflected in-game by the two sharing similar Q abilities, "Steel Tempest" and "Mortal Steel". The move involves a single powerful sword stab, but when landed twice, the brothers can each perform an empowered version that knocks their opponents skyward. Yasuo fires off a long-ranged projectile resembling a tornado, and Yone dashes forward with a powerful cross slash that knocks up enemies right in front of him.
• Street Fighter: Practitioners of Ansatsuken ("Assassination Fist") and its derivative styles all share variations of the three same special moves: the Hadoken, the Shoryuken, and the Tatsumaki Senpukyaku. Compare Ryu and Akuma for example; Ryu's Hadoken set the precedent for other characters' usage, being a simple fireball that travels straight forward at varying speeds and powers. He can also power it up to stronger variants like Shinku Hadoken ("True Void Surge Fist"), Shakunetsu Hadoken ("Scorching Surge Fist"), Denjin Hadoken ("Electric Blade Surge Fist"). Akuma can perform Shakunetsu Hadoken as well as his own version called "Gohadoken" ("Great Surge Fist") which imbues it with dark power. He can also perform one-handed Gohadoken in the air, something other characters including Ryu haven't mastered, which shows just how proficient he's become with the technique.
• Super Smash Bros.
• Tekken