* Older brother: Tua
* Younger brother: Teina
If you're not sure about the age difference, or you want to be more general, you can use teina as it's the more common word.
Here's an example:
* "My brother is coming to visit" could be said as:
* "E haere mai ana taku tua ki te toro." (My older brother is coming to visit)
* "E haere mai ana taku teina ki te toro." (My brother is coming to visit)