The son of late Labour politician Carl Sargeant has succeeded his father in the Welsh Assembly.
Jack Sargeant, 23, triumphed at the by-election in Alyn & Deeside as Labour retained the seat.
He had said he would fight to represent local people "in the proud tradition of my father" and vowed to find out the truth behind his father's death in an apparent suicide in November.
Mr Sargeant Snr, 49, had been suspended from the party and dismissed as a Welsh Assembly minister following unspecified allegations about his personal conduct.
An independent QC-led inquiry has been launched into how first minister Carywn Jones handled the sacking of Mr Sargeant, while an inquest into the late minister's death at his home in Connah's Quay, Flintshire, has been opened and adjourned.
Standing against Mr Sargeant Jnr in the by-election were former district nurse and social worker Sarah Atherton (Conservative), bank worker Donna Lalek (Liberal Democrats), Wrexham councillor Carrie Harper (Plaid Cymru) and environmental campaigner and charity worker Duncan Rees (Green Party).
Ukip did not field a candidate despite having come third with 17.35% of the vote in the seat at the Welsh Assembly election in 2016.
The party said it would not contest the by-election if Jack Sargeant was a candidate, "out of respect to the late Carl Sargeant".
Jack Sargeant, the son of late Labour politician Carl Sargeant, spoke of the "toughest time" of his family's life after succeeding his father in the Welsh Assembly.
In his winning speech following the Alyn & Deeside by-election, Mr Sargeant said: "I want to say a big thank you to every person standing in this room tonight, everyone across Wales, across the UK and across the world as well who have stood by my family during the toughest time of our lives.
"I really can't bring together the words to say thank you enough, but it just means so much to me and I know this special community in Alyn and Deeside and special people have helped all of us so much, and I don't think we would get that anywhere else."
He added: "Of course we are all still devastated by dad's death, the family completely, but it's not just the family - it's everyone. We have been knocking on the doors in the constituency but it's even further afield than that in Wales and across the UK.
"I know that he was loved by so many people and he loves you all so much as well, so thank you for that. I know that our grief will continue but we have got strong support from so many people which means so much again to me."
PA
