The Kidd Pirates had gotten badly injured in their last battle, and all ended up falling unconscious as a result of their injuries. You had good medical knowledge paired with experience, so you took the pirates in and tended to their wounds.

When the crew woke up, they noticed that they were in a forest clearing, bandaged and feeling a lot better. You sat there quietly reading on top of a rock. You didn't see them waking, but the words "Join my crew" from what Eustass Kidd was saying quickly caught your attention.