Arlong

Bellemere is Nami's foster mother. However, the foster family (Nami, her sister Nojiko, and Bellemere) were impoverished. One day, Arlong invaded Cocoyashi village (the name of the village which Nami grew up in) and demanded a tax from everyone. Children had to pay 50,000 berries each, adults 100,000. Anyone who couldn't pay would be executed. Then, Nami's family was discovered... with only 100,000 berries. Bellemere paid the tax for her two foster daughters, on the condition that they were left alone. With this, Bellemere died. In the dub, Bellemere was "sent to the dungeon" because 4KIDS refused to show any character's deaths, regardless of how important it was to the plot.

Arlong is a cruel Merman pirate captain. He will do almost anything to get a lot of money. He has enslaved the village that Nami lived in as a young girl. On top of that he kidnapped Nami and forced her to make maps for him and his crew. It's been 8 years since then.

Arlong promised Nami that if she paid 100,000,000 berries, he'd set her and Coco village free. But when Nami had just about reached that amount (needing only 70,000 more berries), Arlong teamed up with the Navy and stole the money from the poor girl!

Arlong has committed these and more heinous deeds and is shameless to them all.

The first episode of the Arlong arc was Episode 31 "The Most Wicked Man of East Blue, Arlong of the Mermen Crew". He used to sail on the Grand Line with Jimbei (who would become one of the seven Shichibukai) to whom he was an equal to. For reasons (yet) unknown, Arlong left Jimbei's side to split off to create the Mermen Pirates.