Robert Bateman, (known as Bob) (36) and his wife, Paula (35), who was one of the rear passengers, died at the scene of the crash on the A142 between Chatteris and Mepal just after 8pm on Thursday (September 3).
The couple, of Westfield Road, Manea, March, had two daughters, Lexi aged 10 and 18-month old Elizabeth, in the car.
Both girls have since been discharged from hospital.
Fundraiser Shane Yerrell set up a JustGiving fundraising page for the girls after speaking to Mr Bateman’s sister.
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The page has already raised thousands of pounds after the initial £1,000 target was quickly passed.
Mr Yerrell said: “When reading the story about the accident online. I felt gutted for them.
“The children are now left without both of their parents.
“Plus they were in the car at the time so they’ve had to witness it too. It’s so heartbreaking.
“I don’t know the family. But I’ve been fundraising since 2011 and have often raised money for people I’ve never met.
You don’t have to know someone to be affected by their story.
“I can’t bear to see anyone suffer. Which is one of the reasons why I set up Through The Fight Foundation. (www.throughthefight.co.uk)
“I noticed that Robert’s sister had commented on another article online.
“So I messaged her to offer my support and explained that I run a charity, this is what I do. She was happy for me to go ahead.
“The page is going well. No matter how much is raised it’s not going to change the fact that two children are without their parents. But I hope it will help towards their futures or anything they may need growing up.”