He didn’t just spring fully-formed onto the docks of Port Royale. The social circle of pirates is shockingly small.
Jack Sparrow was born in the middle of the Indian Ocean during a typhoon.
The son of Captain Edward Teague and his unnamed pirate wife, Jack grew up in the life, bouncing between calling the infamous Shipwreck Cove home and being a cabin boy for his Pirate Lord (Lady?) Grandmother.
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In his teens, Sparrow captained his first ship, the Barnacle.
Though barely a fishing fishing vessel, it was love at first sight. In the grand tradition of pirates, the Barnacle was commandeered from Tortuga by young Sparrow and his "friend" Arabella Smith. With a motley crew, including a young nobleman by the name of Fitzwilliam P. Dalton III on the run from an arranged marriage, they sailed the Caribbean for fortune and adventure.
Turned out Dalton was James Norrington's cousin.
During a sea battle between his father and young Jack Sparrow when Norrington was a child , James was knocked overboard. Saved by Captain Teague —because pirates have honor and who brings a kid to pirate fight — instead of gratitude James's father replies he'd rather his son have drowned then owe his life to a pirate. Suddenly Norrington's disdain towards Jack and willingness to shoot first makes way more sense.
In the end, rogue pirates destroyed the Barnacle.
You know that Code everyone goes on about? Rogue pirates had no code and were running roughshod over the seas, slaughtering whole crews and plundering without a care. In the end they were dealt with by the Brethren Court but not before irreversible damage had been done to the reputation of pirates as a whole.