Wiremu, 19, and Michael Curtis, 22, were found guilty of murdering the Rotorua toddler in November last year.
Nia died on August 3, 2007 from brain injuries after the pair kicked her in the head.
During a four-week trial the jury was told of how Nia was subjected to horrific abuse, including being swung on a clothesline and placed in a tumble dryer.
Nia's mother, Lisa Kuka, 35, was found guilty on two manslaughter charges relating to a lack of protection of and failure to seek medical help for her critically injured daughter.
Nia's cousin Michael Pearson, 20, and Michael Curtis' partner Oriwa Kemp, 18, were found not guilty of manslaughter.
They were convicted of wilful ill-treatment and various assaults on Nia.
All five were due before Justice Judith Potter in the High Court at Rotorua today.
