Francis Goncalves, who lives in Cardiff, said his brother, Shaul, 40, father, Basil, 73, and mother Charmagne, 65, all started to feel unwell on the weekend of 10 July, which was a few days after they all had a meal together. Within two weeks of their symptoms starting, they had all died.
Francis said his family, who were in Portugal when they died, did not get their Covid vaccines because they had been scared by anti-vaccination "misinformation".
He hopes that sharing his story will save lives by encouraging others to have their jabs.
Francis said: "Dad went to hospital on 6 July for kidney stones, we think he picked Covid up there.
"On 8 July, my parents had dinner at my brother's apartment he shares with his girlfriend and they started to feel very ill that weekend.
"On the Monday, my brother's girlfriend said Shaul could feel something was wrong. He said he'd never felt anything like it, that he felt like he was filled with weight and that he was tired. He decided to get a test for Covid and they tested positive.
"My parents were really ill at the time as well. They went to hospital and I had a text from my father that afternoon saying they've been admitted into the hospital because they have both tested positive. That was on July 12."
With Francis being so far away in Cardiff, he said it became difficult to get hold of his parents, and a few days later he discovered his dad, who had underlying health issues, had been moved to the intensive care unit.
Francis made plans to fly over to be with them in Portugal after each family member started to deteriorate.
"On the Saturday (17 July) I had a message at 8.08pm to say Shaul had been rushed off to hospital in an ambulance," he said.
"I spoke to his girlfriend and she was really worried. Then, at about 1am I received a call from her saying she had been told he had passed away that evening."
Francis said his brother was the "healthiest person" he knew and believes the vaccine would have saved his life, adding: "If he wasn't working out in the gym or running, he was going on walks. He hadn't drunk in 15 years and ate a whole foods plant-based diet."
With his brother being Francis' only means of contacting his parents, Francis then had to get hold of a law firm in Portugal to help him out. The firm contacted the hospital on his behalf and passed on his contact details.
On Tuesday 20 July, the hospital called Francis to say his father had also died.
The next day, Francis managed to get a flight to Portugal to see his mother and to make arrangements for his dad and brother.
However, when he arrived he discovered his mother - who had a number of underlying health issues, including an autoimmune disease - was struggling to cope with the virus.
He said: "They allowed me to go and see her which was already a sign that things weren't going well and I had to dress up in full PPE.
"Then on the Saturday, JuIy 24, I received a phone call from the doctor saying they were in a situation where they had tried everything and the next couple of hours would be critical. Later that evening, I received a call to say she had passed away."
All three members of the family were buried next to each other at a cemetery in Lisbon called Sao Joao, where a section is dedicated to covid-related deaths, on Sunday 1 August.
Francis said: "They said the entire time during Covid they'd never had three bodies brought in together from the same family."
Francis described his experience as "incredibly painful."
He said his family was "small and close" but that his mum, dad and brother had all positively impacted the lives of many others around them.
Speaking about his family, Francis said: "My father gave everything. He would wear broken shoes so we could have the best they could get. I found a bible he carried around with him when I was in Lisbon and I opened it up and saw a bookmark and it was a picture of my mum when she was in her 20s.
"I could see that he loved her and she loved him. He never knew his father, but he always tried to be something more. My mother was a mother hen and she'd do anything for us.
"My brother was my best friend. He always looked out for the best interests of people around him and he wanted to teach people.”
Although talking about his experience is extremely tough, Francis said he hopes that sharing the painful experience might encourage others to get the Covid vaccine if they have so far been too afraid to get it like his family.
Francis said: "They got caught up in a lot of the anti-vaccination propaganda that's going around.
"It preys on people who are afraid and they fall into the trap. The message I want to get out is why would the government want to hurt you by giving you a vaccine? What is the purpose behind it? I've spoken to so many people who are terrified of the vaccine and it costs lives."
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