Charachter(s) like Rin Okamura

He's a lot like Haru from My Little Monster... they even look kind of a like. Haru is rash, random, doesn't think things through, perverted, idiotic, nice, thoughtful at times, and hilarious.

Idk about the personality but Gray Fullbuster looks a lot like him even more than his brother Yukio XD

I find his personality similar to Natsu :3

Luffy (One Piece)
he is also cheerful, he can be an idiot but can also be very cool, loves his big brother, sometimes thoughtless, sometimes gentle and ... perfect!

Edward Elric. I've watched both him and Rin, and they are similar. Ed is really funny but also cool, thoughtful and not about some points at the same time, and is willing to do anything for his little brother, anything... perfect <3