He is the country's first High Commissioner to Australia and is based in Canberra.
In his early 20s he joined the Tonga Defence Services.
He is no stranger to politics, having been the country's appointed Prime Minister in 2000.
Prince Tupouto'a also held the defence, foreign and aviation portfolios.
He resigned from his role as Prime Minister in 2006 - the year the riots took place in Tonga's capital, Nuku'alofa, under the reign of then appointed Prime Minister Dr Feleti Sevele.
Some say he bowed out because of political unrest and anger among the people - calling for a more democratic Tonga. Others say it was because of his involvement with the doomed Royal Tongan Airlines - which led to the country losing millions of dollars.
Auckland-based Tongan church leader Reverend Sitili Tupouniua said his political experience and his mistakes would only make for a better king.
"He's the right man. When he was the Tongan Prime Minister, he was young. But he's experienced now.
"He's reliable and he's very good in trying to help the Tongan people."
Auckland lawyer Joel Fotu said many were hoping that the new king would continue the work of his late brother in seeing that the country is a democratic one.
"I think everybody hopes he will keep with what his brother has done ... the people like that," Mr Fotu said.
"He might see the momentum and see it through."
Crown Princess Nanasipau'u is well-respected among the people and could therefore be a key influence to her husband's reign as king.
Tongan community leader Will'Ilolahia said: "I think his wife will have a good influence on him. She's really people-oriented. If there'll be anything that'll help him, it's her."
Mr Fotu said the fact that Prince Tupouto'a had a wife and children meant that he would arguably be a more caring king.
Last year King George V was caught up in fiery protests with his people based in New Zealand, when he attempted to put the Auckland royal residence - Atalanga - up for sale.
It is understood the Crown Prince did not like the idea, as he felt the property was of value to his children, family and wider Tongan community.
Mr Fotu said: "His style will be different from the previous king because he has a family ... he will be a good king if he keeps the people of Tonga in his mind."
There were varying reports yesterday as to the exact cause of the King's death, with kidney and liver problems both suggested as likely causes.
