Being Luffy's "sibling" wasn't too bad. He was always there for you. He always made you laugh. And you both shared the power of the Gum Gum Fruit after eating it as children. Now, your bodies are made of rubber. Cool! Except, neither of you can swim, or even be near water because it weakens you. And Buggy knew that...that's why he had both of you in a tank that was filling with seawater, and you'd both die if you didn't tell him where the map to The Grand Line was...