Matthew Moore, aged 48, ran in the event last year and enjoyed it so much that his wife, Jenny, aged 47, has also signed up for this year's challenge.
The couple both work for The Smile Centre Dental Practice in Whitchurch Road and although not club runners have always enjoyed keeping fit.
Matthew said: "I ran the marathon last year and wanted to do it again for charity.
"I will be running for The Outward Bound Trust while Jenny will run to raise money for Guide Dogs.
"My father, Alan, aged 78, who lives near Sheffield is registered blind but does not have a guide dog.
"We also have a two-year-old fox-red Labrador named Rufus and I think that is why she chose the charity.
"We have done a few half marathons in the past and used to run when we had more time."
Meanwhile mother-of-two Jenny, aged 47, said: "We both met at Birmingham University while dental students and graduated in 1999.
"We have been working together for about five-and-a-half years.
"Mat took part in the marathon six months ago and had such a wonderful time and we decided it would be good to run together and raise money for charity.
"We are not very fast and just hope to finish and get the medals at the end.
"Last year myself and the children went to support Mat but ended up walking a half marathon trying to keep up with him.
"I think that this year they will be staying at home with the grandparents."
Anyone wanting to donate as sponsorship for Jenny can do so via her Jennifer-Moore23 justgiving page.
Sponsorship for Matthew can be given via the website https:2023tcslondonmarathon.enthuse.com/pf/matthew-moore website.
People can also place donations in collection boxes at The Smile Centre.