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".