"Your grandfather was not only great singer and sax player, he was the best Nazi killer I have ever seen. He was a magnificant Inglorius Bastard, and look at you, just like him.Errrr Except your a scythe instead of a shotgun."-BLU Soldier talking to Soul about his days killing Nazi with Soul's grandfather
Shawn "Shark Toothed" Evans was Soul's grandfather, a talented jazz singer and sax player, and a weapon (he turned into a shotgun). BLU Soldier and Pilot knew him as part of their gang of Nazi hunters in WWII known as The Inglorius Magificent Bastards.
Shawn was famous in America as a singer of scat and played a mean Saxophone. Dressed in a fancy black and white zoot suit and fedora, women swooned over him, men wanted to be him, his career would later lead him to meeting Soul's grandmother. He wanted to join the military during WWII but they rejected him for being a weapon (they called him a "freak") and BLU Soldier-Jane Doe-found him outside of the recruitment center cussing out the officer throwing his fedora on the ground. Doe asked him if he wanted to come along with him to Eroupe, joining him and the BLU Pilot-Monty Watson-and a few other individuals, they formed The Inglorius Magificent Bastards. By the time the war was over, Shawn had taken a bullet to his right lung, he couldn't sing only play. He was furious about the bombing in Horshima saying killing innocent people and fuled with bigoted propaganda of the Japanese disturbingly similar to Nazi propaganda about the Jews as "Uncool, Unlegit, it just 'aint right.". Shawn died not to long after his grandson-Soul-was born, but being stubborn as he was he continues to watch over his grandson as a wondering soul. BLU Soldier also make sure nothing bad happens to Soul as a repayment to his old freind. Soon Soul's old old man would become a "Soul Battery" for the Retro Ace's armour wich can allow him to go into "Soul Singer Mode" where the armour becomes black, white and bits of crimson while his raygun "The Rightous Bison" turns into a AA12 with piano key patterns and Shawns eyes on the Barrel. How they encountered each other was when Shawn as a ghost resembling his youthful self got into a fist fight with Isley to protect his grandson and Maka none of the group knew who the man was but he gave Isley a beatdown while blues singing insults, he bonded to Ace's armour as a soul and can project himself as a hologram through the armour along with the ghost of Luffy's deceased foster brother Portigas D. Ace. With him as one of Retro's Familiars, Retro can go into "Sound Mode"