Do you know what Oni-chan and One-chan mean? 

Onii-chan and Onee-chan is nothing more than an informal way of speaking older brother and older sister. 

Onii [お兄] literally means older brother and Onee [お姉] means older sister. Chan, on the other hand, is a child treatment honorary, informed and intimate, as if he were a diminutive (little sister).

The most formal and common is to use the suffix san, so we also listen a lot to the words onii-san for older brother and onee-san for older sister. 

There are other ways to speak brother in Japanese like:  Kyoudai Shimai Ani Ane  Otouto Imouto Futago Gitei Gimai Each shape is specific to something like age and sex.