The family was dealt another devastating blow when Dean's brother Darren, 42, died from coronavirus in intensive care on November 2.
Lewis has since spoken out, describing the situation as "devastating" – particularly for her father-in-law.
"My father-in-law is broken. He has lost his wife and his two children," she told the BBC.
"He keeps on saying to us, 'It should have been me, it should have been me.'
"It's so difficult to try and help him, and hold me and my children together because my children are absolutely devastated."
The mum-of-three issued a warning for those who thought Covid-19 was "a big joke".
"People need to wise up," she said.
Lewis's message comes as England entered a four-week lockdown on November 5 due to rising numbers in a second wave of the virus.
Wales is also in a second lockdown known as a "firebreak" which began on October 23.
'Stuff of nightmares'
Family friend Alison Higgins has now launched a fundraising campaign and raised over $8000 to cover funeral costs.
"This is the stuff of nightmares. It's incomprehensible what's happened," she wrote on the GoFundMe page.
"Knowing how much fundraising the family have done over the years, it was only right we came together for them."
The hospital where mum Gladys and her son Darren – who had Down syndrome – died has been the scene of a coronavirus outbreak linked to 51 deaths, The Sun reports.
For a period in late September, the hospital had to close its doors to almost all new admissions – although those restrictions have now been relaxed and infection rates now appear to have stabilised, according to a report by the BBC.