Jonathan Bloomer is the chairman of the Morgan Stanley International bank and insurance company Hiscox.
The 70-year-old Briton was educated at Imperial College London and has previously served on a number of company boards.
Mr Bloomer appeared at trial as a defence witness for Mr Lynch, according to the the Financial Times. Media reports suggest the pair are close friends.
Mr Bloomer’s twin brother, Jeremy, told the BBC he felt numb and his family were “coping the best we can” as rescue workers continued to search for his sibling.
“He was my elder by half an hour, so, it means a lot when you lose a twin brother. We’ll still wait and see, so it’s fingers crossed,” he said.
He added: “It’s a slow process, and it will take time. There might be air pockets but we don’t know.”
Aki Hussain, group chief executive of Hiscox, which Mr Bloomer has chaired since 2023, said: “We are deeply shocked and saddened by this tragic event.
“Our thoughts are with all those affected, in particular our chair, Jonathan Bloomer, and his wife Judy, who are among the missing.”
Family await news of man on sunken luxury yacht
Judy Bloomer, charity trustee and supporter
Judy, the wife of Jonathan Bloomer, is also among the six people missing.
Ms Bloomer is listed as a former director of property developer Change Real Estate along with her husband.
She has been called a “brilliant champion for women’s health” by a charity she has worked closely with.
Ms Bloomer has been a trustee and supporter of gynaecological cancer research charity the Eve Appeal for more than 20 years.
The charity’s chief executive, Athena Lamnisos, said she was “deeply shocked to hear the news that our very dear friend and her husband Jonathan, are among those missing”.
“Our thoughts are with Judy and Jonathan’s family, as well as all those who are still waiting for news after this tragic event,” she added in a statement.
Who has been rescued?
Among the 15 people who were rescued are nine members of the yacht’s crew.
This means every member of the crew is accounted for minus the chef, who local authorities say has died.
Eight of the 15 who were rescued have been taken to hospital.
Dr Fabio Genco, who was part of the local emergency medical service that treated the survivors, said all of them had been discharged from hospital by Tuesday.
A British mother, named locally as Charlotte Golunski, was travelling on the yacht with her partner and baby girl. All three were rescued from the boat.
In an interview, she described holding her infant daughter above the surface of the sea to save her from drowning.
Ms Golunski is a partner at Mr Lynch’s company, Invoke Capital, where she has worked since 2012, according to her LinkedIn profile.
The Times has reported that she has previously worked for Autonomy, the company at the centre of Mr Lynch’s recent court case.
Another lawyer, Ayla Ronald, was also rescued along with her partner.
The New Zealand national works for Clifford Chance, where Mr Morvillo is a partner, and was part of Mr Lynch’s legal team for his June trial.
Her father told the Telegraph that she was “invited to go sailing as a result of the success in the recent United States court case”.
Angela Bacares, Mr Lynch’s wife and Hannah Lynch’s mother, is also among those who have been rescued.
On Monday, Ms Bacares was using a wheelchair after suffering abrasions on her feet, according to the newspaper La Repubblica.