Jack (ジャック) was the son of Drachma who died years prior to the events of Skies of Arcadia. Were he still alive, he would've been the same age as Vyse (17). He is the namesake of Drachma's flagship, the Little Jack.
While hunting for the arcwhale Rhaknam in the Valua region, Drachma tells Vyse about Jack. Back when Drachma ran a fishing boat in the North Ocean, Jack would come along to help out and learn to become a sailor, earning the nickname "Little Jack" from the other sailors.
One day during an otherwise normal fishing trip, the ship came under attack by Rhaknam. The small fishing boat had no chance against the powerful arcwhale and was destroyed; while Drachma managed to survive the encounter (albeit with the loss of his right arm and eye), both Jack and the rest of the crew perished. It was from that moment on that Drachma vowed to hunt down and kill Rhaknam to avenge his crew and his son.
One of Jack's hobbies was collecting feathers, a box of which Drachma kept as a memento.