The 56-year-old -- former world champion at two weights -- said Mark had been the "Joker" of the family.
The British champion was due to put his WBA, IBF, WBO and IBO belts up for grabs against Bulgarian challenger Pulev at the Tottenham Hotspur Stadium in London on June 20.
Joshua's title defence against IBF mandatory challenger Kubrat Pulev was scheduled for June.
Following a controversial draw in December 2018, Fury overpowered Wilder in Las Vegas in February, beating him in seven rounds.
The British fighter released a video on social media using a punchbag to describe how to "hit her on the chin".
Yarde, who fought Sergey Kovalev for the Russian's cruiserweight world title last year, said his father had been "fit with no health issues".
Using a punchbag, he then describes how to "hit her on the chin" and "finish her off".
Turkey's boxing federation criticised organisers of the event after three fighters and a coach tested positive for COVID-19.
Khan is ready to hand over the keys to the 60,000-square-feet (5,600-square-metre) venue in his home town of Bolton as concerns grow over bed shortages.
The Boxing Road to Tokyo event started on Saturday and was scheduled to run until Tuesday behind closed doors. But it was suspended after three days over growing coronavirus fears.
Charles, the eldest son and heir to Britain's Queen Elizabeth II, is showing mild symptoms of coronavirus and is self-isolating in Scotland.
With travel restrictions affecting both the US and Britain, and Las Vegas' casinos shuttered, Arum said a postponement was the only sensible option.
European Boxing Confederation (EUBC) president Franco Falcinelli said he feared the risk of a boxer getting the virus was "very high".
It was alleged in a Mail on Sunday report a farmer was offered money to provide an alibi for Fury's failed drugs test in 2015.
The tournament is planned to be held on November 2-9 in the Hala Legionow sports complex with capacity 3000 spectators.Â
