Bio: Grey Fox is a FOXHOUND agent and a friend of Solid Snake, introduced in Metal Gear.
In Metal Gear, he disappears after sending a cryptic message about a "METAL GEAR," and Solid Snake, the protagonist, must save him and learn from him about the enemy super-weapon, codenamed "Metal Gear". Throughout the course of the games events Grey Fox is the mentor of Snake and teaches snake most of the abilities that later become staples of his infiltration style. They are also long time war-buddies afterwards and as stated by snake, best friends. However it is an unwritten rule between them that their personal life is not mentioned to either.
In the sequel, Metal Gear 2: Solid Snake, Gray Fox once again disappears, but turns out to have defected to the side of the antagonist, Big Boss. However, Gray Fox secretly assists Snake by leaving him anonymous tips over his radio. Solid Snake confronts and seemingly kills Gray Fox in a final fistfight to the death in a minefield. In the original MSX2 version, his character design was modeled after the likeness of actor Tom Berenger. In later re-releases of the game, Gray Fox was redesigned to be more in-line with Yoji Shinkawa's depiction of Fox in later games. According to Metal Gear 2: Solid Snake, Frank is born from German-American and Vietnamese parents, Frank's parents died during the Vietnam War while he was still a child.
Metal Gear Solid: Portable Ops, set in 1970, expands on Gray Fox's past (integrating elements of the Cyborg Ninja into it), featuring a teenage Frank Jaeger as a masked machete-wielding member of the FOX unit code-named Null. Four years prior to the events of the game, Naked Snake became acquainted with him as a nameless child soldier in a guerrilla group in Mozambique. Naked Snake took the young child and left him in a rehab center, in which he was then taken by the CIA and used as a test subject for the Perfect Soldier project. He fights Naked Snake twice during the game before joining him once he is defeated.
Fox's last name, Jaeger, is German for "Hunter". This fact has been played upon in several of the games. In Metal Gear 2: Solid Snake, Natasha Marcova tells Snake that she once fell in love with a man named Frank Hunter; during the later fight with Fox, Snake's mercenary expert Kasler tells Snake that Fox's real name is Frank Jaeger, and that mercenaries knew him as the legendary Hunter because of his last name. Also sometime before Metal Gear and after Portable Ops, Fox was fighting in mozambique and apparently killed two people in a friendly fire incident, one man and one woman. He then later found the daughter of these two people as a starved orphan by the Zambezi river. She was presumably aged 3-5 at the time. Fox Adopted her as his younger sister, presumably aged 20 at the time, and named her Naomi Hunter, after his English surname and common alias.