LOVE this question. This answer might be a lot, but it all boils down to the fact that they all have a mutual hatred of bootboys. Ill put the rest of this under the cut.

Gordon was Just A Guy, a single dad and a scholar, who became a pirate when some dudes in the navy chopped off his arm and murdered his son (RIP Joshua) over an uh. misunderstanding. Also because they were domineering power-hungry assholes, but you know how cops are. Coomer was technically* who he met next. He fit Gordon with his hook arm after Gordon told him his story. Coomer told him that he, in turn, was looking for his partner. Helped Gordon steal a dinghy. They started committing Crimes (or well. Gordon started. Coomer’s a crime boy.)

Tommy was next. Tommy had very recently run away from home at that point (with Sunkist, the perfect dog.) Tommy felt very stifled by his life, so he ran away to try to find something…else, but he’s been unblemished by society and the world is kinda terrifying so when Gordon and Coomer try to rob him they, particularly Gordon, feel awful HSJDHJSDH they end up just taking him with them. Teach him how to use a gun. He’s weirdly good at it for some reason? He’s ALSO GOOD at mapping stuff out, reading maps, navigation in general, so this is a no-brainer.

With Tommy on board their little dinghy, the next stop is breaking someone out of jail. Yeah… Bubby. In jail for arson and misuse of explosions. Coomer’s partner in crime and life. REALLY good with guns. It doesn’t take a lot to convince him to join their little team, even if he’s initially pretty pissy that it wont just be him and Coomer from now on. With Bubby’s help, they all steal a ship and leave the island where inmates are kept.

They’re pirates. They wear this with pride. Their crew is small, but they like it that way, and they’re GOOD at it. They do what they can to fuck up the system, loot and steal and kill when necessary. Anything to survive. They become a tight-knit family. It isn’t hard to care about one another. Coomer and Bubby get married on the ship >:]

Also important to note that while Benrey IS a stowaway, they’ve actually known Tommy for a very long time… hm!