Alastor Moody was known for many things during his lifetime. War hero, paranoid bastard, Head Auror, a close friend to Albus Dumbledore himself, baby brother, and god-father. The last two on this list may give the average person who has interacted with the man pause. As family trees are significant to the wizarding world, folks in the know would be aware that Alastor Moody was an only child. As for the last thing on the list, who would give that man rights to a child in their right mind? The answer to both is Charlus Fleamont Potter.
Charlus Potter was two years ahead of Moody in Hogwarts and in a rival house, but that didn't stop him from adopting Moody as his little brother in his first year. Charlus mentored young Alastor throughout his Hogwarts career, and upon graduation, Alastor followed Charlus into the Auror Corps. Years passed, and Alastor served as the best man at Charlus's wedding to Dorea Euphiema Black. When the couple had their only biological child James Charlus Potter, Alastor the first choice for a god-father, when that boy came home for Christmas from his first year at Hogwarts with three other boys, Moody became "Uncle Alastor" once more. Not everything was picture perfect, however. A dark lord was rising in Europe, whose violent acts were vile enough to scare the public into not mentioning his name. Charlus, as head Auror, became a target for that despicable creature and his followers, the death eaters. Alastor and Charlus did everything they could to make sure he and the family were as safe as possible. The two worked with Dorea and the boys until they could set up a safe living place and excelled at dueling. During which time, the boys nicknamed Alastor Madeye. By the time the boys graduated from Hogwarts, James and Sirius Joined the Auror Corps and quickly rose to the top. While Peter joined the Ministry Portkey office, Remus became Alastor's eye in the Werewolf camps and helped turn many wolves away from the dark lord.
Two weeks before the horrific Halloween, death eaters poisoned Charlus and Dorea with dragon pox. They died upon exposure. That same day over fifteen death eaters attacked Moody outside of the ministry. Moody survived, but he was knocked into a coma for nine years and lost his leg and eye in the fight.
A week after his release from the hospital, Albus, many middle names Dumbledore, visited him. After some confusing small talk, Albus gave him an address to the man he wanted to be the newest DADA Professor. When asked why Albus wanted him to speak to the man, Albus explained that he hadn't been able to contact the man since the war, and neither has any one of the man's friends. Alastor quirked an eyebrow and commented upon the stupidness of that decision. Dumbledore beamed at him and told to inform the man of that when he saw him and then Flooed away.