President Rodrigo Duterte's youngest son has also joined politics as he filed his certificate of candidacy (COC) as vice mayor of Davao City on Wednesday, the last day of filing of COC for those who will run for the May 2019 elections.

Sebastian will be the running mate of his elder sister Davao City Mayor Sara Duterte-Carpio.

The mayor, in an interview with reporters after joining her younger brother in filing his COC at the Commission on Elections in Davao City, defended her family for virtually being now a "political dynasty."

"We really cannot deny that (political dynasty)," Duterte-Carpio said, adding that she already expects their detractors that her family would be called as a political dynasty.

Paolo Duterte, eldest child of the President with former wife Elizabeth Zimmerman, had filed his COC as congressman of the First District of Davao City.

He was Duterte-Carpio's vice mayor, but he quit on December 25 last year after he was accused of an involvement in a drug smuggling case at the Bureau of Customs and after his public quarrel with his 18-year old daughter. Paolo denied any involvement in the illegal drug smuggling at the BOC.

"Yes, it is a political dynasty. But in the sense, we are submitting ourselves in a democratic process," Duterte-Carpio said.

She added that a political dynasty does not only happen in Davao City but in other parts of the country and even abroad as well.

She said Sebastian consulted their father before finally deciding to join in the politics.

Sebastian admitted he has no experience in politics.

"As I said, I don't have any experience in politics, but I grew up in politics," the neat-looking presidential son told reporters after filing his COC.

Sebastian, the hunk and surfer son of Duterte, used to have long hair. He is also a member of a local band in the province.

He said he is not expecting anything with his entry into politics.

But he promised to deliver the needed services of his constituents once he wins in the elections.

Asked of the advice of the President and of his family with his decision to run for a public office, Sebastian said, "There's nothing much. I was only told to do my job well."

Duterte has served Davao City as its mayor for about two decades before running for president in 2016 elections. Celerina Monte/DMS