User blog comment:Neowitch/Paranoid Similarities/@comment-3986064-20120131145039

We can even take it like this:
 * Luffy and Chopper are both childish being even unable to recognize Sogeking
 * Zoro and robin are both very serious and they both seem to be the only one that would really kill someone
 * Nami and Franky are both exhibitionists, and if you remember, Franky spent all the money he ever got, even those 200 mil beli in 1-2 days, whilst Nami would be very careful with the money, not to forget that they are both thieves(although Nami is clearly the bigger one)
 * Usopp and Brook is exactly what DP just said
 * Sanji and Jinbe, fire and water, gentleman wanna be and gentleman, even Robin called Jinbe a ladies man, both fought together in the last arc

I just mentioned some interesting facts about the 1st till 5th that joined in the Blue Sea and the one that joined on the Grand Line.

You can look at it in many more ways, they could even be us thinking too much, coincidences or oda's awesomeness

PS:Jinbe unofficially joined if you didn't notice