Aye. Whitebeard crew. First division commander, and acting captain temporarily.

If you see anyone with this tattoo, you can know they're my family; nakama. [Gestures to the blue cross and crescent moon as his chest.]

Ace is 2nd division commander, and Luffy's his little brother, captain of the Straw Hat crew. Nami, Sanji, Robin and the others are part of that crew. Have you met Doctor Law?