Hunter Biden, candidate's son at centre of Trump's impeachable effort to bring down his father, speaks at DNC

Former vice president's last living son, who has remained out of the spotlight as he became central figure to president's impeachment, introduces his father to accept party's nomination

Hunter Biden, who has remained out of Joe Biden's spotlight as his father sought the presidency, made a rare public appearance at the 2020 Democratic National Convention to introduce the Democrats' nominee to face Donald Trump.

In a video with his sister Ashley, the siblings called their father "the strongest shoulder you can lean on" and "rocksteady" before letting Beau Biden, their sibling who died in 2015 following a brain cancer diagnosis, have the "last word" on their father.

The segment cut to Beau Biden's remarks from the 2012 DNC: "In moments both public and private, he's the father I've always known, the grandfather my children love and adore, my father, my hero."

Their appearance followed an introduction from the former vice president's granddaughters, part of a Thursday event that highlighted the candidate's family connections and his humanity, as a father and grandfather as well as a compassionate colleague, according to the people who have run against him and worked alongside him at the White House and in Congress.

It was an extension of candidate Biden's personal brand of politicking, relying on a narrative of mourning and an empathetic dynamic with voters who also have endured pain and loss. Mr Biden's first wife Neilia and infant daughter Naomi were killed in a car accident in 1972.

Hunter Biden, the former vice president's last living son, has grieved alongside him, while his private life has been mired in controversy as he struggled with sobriety and emerged as a central figure in the president's impeachment and Republicans' retribution.

The House of Representatives impeached the president last November, after investigations revealed that Mr Trump had pressured Ukrainian officials to investigate the Bidens, including Hunter, who served on the board of a Ukrainian energy company.

A whistleblower's report of the president's phone call with Ukrainian president Volodymyr Zelensky in July 2019 – in which the president suggested withholding congressionally approved funds in exchange for information on the Bidens' ties to energy firm Burisma – prompted House Democrats to investigate. The Senate acquitted the president, who has declared the findings and impeachment a "hoax".

Thursday's event also included two moving tributes to Beau Biden, who served as Delaware's attorney general.

Hunter Biden has shared less of his father's spotlight through the years, compared to his politically aspirational brother, but he is now scrutinised by the president's allies, connecting him to allegations of corruption in Barack Obama's administration in both Ukraine and China. The GOP-controlled body also has sought to investigate Hunter Biden's work in Ukraine.

Joe Biden's campaign has called the probe a "craven, previously debunked smear" against the candidate.

The president has led chants of "lock him up" and yelled "where the hell is he?" during campaign rallies, echoed across social media by right-wing allies, and he has called the Bidens "stone-cold crooked" and a "disgrace" while his sons Donald Trump Jr and Eric Trump have also turned the controversy into campaign fodder.

"I don't really think about Donald Trump's kids that much," Hunter Biden told ABC in 2019. "They seem clownish, to me, when I see them. It's all noise."

He said he was "shocked" when he discovered he had been at the centre of the president's phone call.