Ngapera logged into her Facebook account and looked at the messages, before talking about them with Te Wao-Titi.
He then invited the complainant to the house, pretending to be his partner.
Still pretending to be his partner, he told the complainant Ngapera would not be home until 3pm.
When the complainant arrived, he was confronted by Te Wao-Titi, before Ngapera came out the back of the house, the summary states.
The men exchanged words, and the pair rushed the complainant before he could leave.
Ngapera hit the complainant with the hammer, before the brothers punched and kicked him while he was lying on the ground.
Ngapera also used the hammer to strike the complainant's torso.
The police summary said Te Wao-Titi had said Ngapera was involved in the altercation when he arrived at the property.
Te Wao-Titi had denied being involved in the assault, and said he intervened to try and stop it.
Te Wao-Titi was sentenced to 50 hours community work. His lawyer, Leo Lafferty, said Te Wao-Titi is about to finish a 90-day work trial and be offered an apprenticeship, and wants to save money for a house.
The Judge said Te Wai-Titi should get his community work done as quickly as possible and put the matter behind him.
Ngapera is scheduled to be sentenced on November 8 in Napier District Court.
