How do you say For my sister in Maori?

This can be said in various ways.

For females, if you were to refer to a sister who is older, you would say "mō taku tuakana". If you were referring to a younger sister, you would say "mō taku teina".

For males, this changes completely. You would simply say "mō taku tuahine".

Mō = for

Taku = my

Tuakana = elder

Teina = younger

Tuahine = sister