Mr Pohiva, the eldest son of the late prime minister, 'Akilisi Pohiva, narrowly won the by-election for his father's former Tongatapu One constituency.
Sioasi Pohiva defeated scientist Netatua Pelesikoti Taufatofua by just 16 votes.
The win was an assurance that people still wanted to see a more democratic Parliament and more political reform, he said.
Mr Pohiva wanted to see the power of the nobility reduced, but he did not necessarily want their seats in Parliament to go.
He said there were several options available.