The pair have lived in New Zealand with their family for six years and were proud to be New Zealand citizens.
Ngonidzashe loves playing rugby and hopes to be an All Black one day.
He said he enjoyed rugby because he could just be a boy, and just have fun.
He said New Zealanders were always friendly and the country was beautiful.
Michelle said New Zealand was a good place to live – "not too hot, not too cold".
"We’re happy that we are part of New Zealand now."
Their father, Abie Mathetha, said they had moved to New Zealand for an improved quality of life.
"We came here because of the beauty and tranquility of New Zealand … It’s so peaceful here," he said.
Eight new citizens were sworn in yesterday, originating from Britain, Ireland, Germany, South Africa and Zimbabwe.
Marlborough Mayor Alistair Sowman told the new citizens their customs and heritage would enrich the society of NewZealand.
He said they should take advantage of the privileges of citizenship that were now theirs, but remember their first allegiance was now to New Zealand.