Alexander had then approached Wano's bedroom with a knife, sparking the confrontation.
There was limited evidence about what happened in that small and narrow hallway but neighbours overhead the violent swearing, the court heard.
Wano's girlfriend had called police to report the stabbing.
Justice Nicholas Davidson said it was unplanned and seemingly came out of nothing.
"You wanted to carry on partying, but after a verbal stoush with Tainui you 'lost it'.
"It is revealing that you told the psychiatrist you felt powerless to rein in your anger due to your level of intoxication."
The court was told of Alexander's troubled youth which included being abused as child and dropping out of school at 15 some time after being diagnosed with ADHD.
"You have spent most of your life on the street."
It seemed Alexander had first tried alcohol when he was just 7 years old, Justice Davidson said.
"You used to commit crimes when you were drunk, but this has been replaced with fighting, which you say you do not remember afterwards."
Alexander had felt an "instant connection" with his brother when they met for the first time and did not understand why they shared the same parents but not the same surnames.
"You have thus lived a life of very limited personal relationships, with few boundaries and I conclude you do not really know what a whānau is or means as you have not experienced it," Justice Davidson said.
Alexander had kept to himself, believing nobody else would look after him, he said.
"While you have written yourself off in a real sense, if you engage with counselling and with your Maori culture, I think there is a different pathway for you," Justice Davidson said.
"If you take it, you will avoid the likely other path which is to spend the rest of your
life in prison.
"I rely on others for my observation that finding your cultural identity is your pathway to a different world than crime, alcohol, drugs and prison, in which you have lived for so long."
What stood out in a report about him was his "extreme remorse for what happened".
It would have been manifestly unjust to sentence Alexander to life without parole, Justice Davidson said.
He needed to address his predisposition to violence, he said.
"You have to believe in yourself, and to do that you must find yourself, and the path lies before you."
