Uenuku Thompson threatened family members with a kitchen knife after being told that his younger sister's boyfriend - who he did not like - was on his way over, the Whanganui District Court was told on Tuesday.
Thompson became belligerent at the news and began to threaten his family.
"I'll stab her if he comes over here," Thompson reportedly said.
He rushed into the kitchen and picked up a knife and began brandishing it around.
"You think I'm crazy, I'll show you crazy."