You, know, the Strawhats are like a big family. Zoro's kinda like Ace, playing the part of the sensible, but "cool" big brother who doesn't like to talk about mushy stuff like girls and feelings.
Robin is the big sister in college who can scare us with just the way she talks, who's aloof and admired, and loves everyone dearly.
Sanji is the family friend from right across the street who everyone's know since they were little, who lusts after the sisters and practically is family anyway. He'll never admit it, but the eldest brother is actually a bit tougher than he is. Although he constantly hits on the sisters, he treats the guys like brothers. (Sorry guys, but that's pretty much true.)
Brook is the freaky uncle who used to be a hippie, acts like a little kid, and messes with everyone, but is actually very kind and talented and just doesn't always show it. (face it, we ALL have one of these)
Franky's dad's best friend. He's dad's drinking buddy, and whenever he comes over to grab pops for Sunday football, the older siblings shake his hand, while the younger ones hang all over him and call him "Uncle Franky". While he waits for Dad to come downstairs, he makes everyone laugh with his ridiculous antics. (again, we all know this guy)
Nami is the younger sister who is sexy and up to date with fashion, brilliant, and who looks up to her older sister a LOT. She doesn't show it that often, and screws with her siblings (except her older sister) constantly, but in the end SHE is the only one who can, and is very protective of them and loves them. The family, especially her brothers, just dote on this one, much as they can't stand her.
Chopper is the youngest son with the shyness complex and the big brain. Everybody relies on him sometimes for help with calculus because he took the class a frickin YEAR before you did. He doesn't have a whole lot of friends because not that many people know him well. This dude's family is his life.
Usopp is the middle son's (Luffy's) best friend, who always hangs out with the younger members of the family, telling crazy stories and making himself at home whenever he comes over. He's got a crazy imagination and is always building wacky contraptions.
Luffy is the middle son, the lovable idiot. Everyone has to stop him from being dumb and hurting himself, and he understands that his family and friends are smarter than him, but he doesn't care. He's the moral compass, and when it gets rocky, his simplicity holds everything together. He doesn't look like that much and people underestimate him, but he's the one who defends the honor of his sisters when Sanji isn't available. In general, if you fuck with his family, give your soul to God FAST, because your ass belongs to Luffy.