Seaborn, 30, was diagnosed with a tumour in 2022, during her pregnancy with her and Sheeran’s second child.
The tumour was inoperable until after she’d given birth; the couple welcomed the child in May 2022.
A forthcoming Disney Plus documentary series titled The Sum of it All sheds some light on Sheeran’s life, his rise to fame as well as his personal struggles.
“Long story short, I got diagnosed with cancer at the start of the year, which was a massive s***ter, but it made me massively reflect on our mortality,” Seaborn says in the series.
Part of this diagnosis formed part of her decision to document their lives for fan consumption. She explained: “I was saying to Eds, I’d never have agreed to do anything like this before – never, ever, ever – but it made me think this whole year, if I died, what’s people’s perception of me?
“What am I going to leave behind? It genuinely wasn’t until this year when I was just like, ‘I might die’.”
According to Seaborn, Sheeran, 33, reacted to news of her tumour by channelling his feelings into his music.
“We had the diagnosis of the tumour and the next day, Eds went down into the basement and wrote seven songs in four hours,” said Seaborn.
“Some people write a diary and get their emotions out through the pen and, for Eds, if something really intense happens, he’ll go and write a song.”
In March, the trailer for the series hinted at the dark times that Sheeran and his family have faced in recent years. A notable moment saw the “Shape of You” vocalist break down in tears over the death of his close friend Jamal Edwards.
The Sum Of It All will be released on Disney Plus on Wednesday 3 May.