Adam Fenton, 31, had been told he was cancer free three weeks before his death on July 28.
He had endured months of gruelling chemotherapy after being diagnosed with highly aggressive B-cell lymphoma.
Mr Fenton had miraculously beaten the disease despite having tumours on his heart, lungs and lymph nodes, which all shrunk after treatment.
But just as he was preparing to move on with his life he was found dead at the foot of cliffs on Newquay’s Towan beach, in Cornwall, at around 6.30am.
He had failed to return home to his fiancee Carly Blackman, 33, and three young daughters, after going out for drinks with friends to celebrate the good news.
He was found by a dog walker and police are treating his death as unexplained.
Ms Blackman’s mum Rebecca Watson, 53, said his death was a ‘mystery’ but did not think Mr Fenton had committed suicide.
Speaking on behalf of her daughter, Ms Watson said: ‘The cancer brought us all closer together. We were going up and down from Derriford Hospital. The tumours were so big. It was so much.
‘We never thought he would come out the other side. But he did.
‘They were about to get married and now the songs they picked for their wedding will be played at the funeral.’
In a cruel twist, Mr Fenton and his family had been on a day out at the spot where he died two weeks earlier and a picture had been taken.
Ms Watson added: ‘Telling the youngest girls was heart-breaking.
‘They’ve been going to and from hospital helping their daddy fight cancer and now this.’
A spokesman for Devon and Cornwall Police said: ‘We were called to the Towan Beach at 6.36 this morning after a male was found on the beach by a member of the public.
‘The ambulance service attended and he was pronounced dead at the scene.
‘At the moment we are treating the death as unexplained.’
Friends are now raising money to support full-time-mum Ms Blackman, and daughters Macie, six, Maddison, five, and Bayleigh, 13, whose benefits have been stopped following Mr Fenton’s death.
Ms Watson claims when the family informed HMRC of his death they mistakenly stopped all her daughter’s benefits.