Nine sisters are hoping to raise thousands of pounds for charity while jogging into the record books.
Sisters set up a website for people to sponsor their marathon feat
The siblings are running the London marathon on Sunday and aim to establish a world record as the largest group of sisters to run the 26.5 mile trek.
The McWilliams sisters - aged 21-35 - are from Limavady in County Londonderry but now live all over the world.
They are aiming for at least seven to cross the finishing line to secure funds for the charity Childhood First.
The sisters - Catherine, Margaret, Antoinette, Olivia, Marian Lucia, Marthena, Carmel, Lisa and Francesca - had been in training in the three continents where they now live.
They said: "We enjoyed a happy and loving childhood and were drawn to run the London Marathon on behalf of this small children's charity in order to help children less fortunate than ourselves.
"Childhood First aims to relieve the suffering of abused, neglected and disturbed children and young people through intense therapeutic programmes of integrated care, treatment and education in both residential and outreach projects.
"We want to play our part in helping provide them with the skills and self-confidence they need to move into the wider community with a sense of purpose and self-respect; put their troubled pasts behind them and go on to lead successful, productive and happy lives."
The McWilliams sisters hope to raise £30,000 for charity
The sporting siblings said they had been "pounding the pavements of New York, Hong Kong, London, Dublin and Portstewart".
"In this, the first recorded attempt by such a large number of sisters to run the marathon, we hope to create a London Marathon record for participating sisters."
They set up a website for people to sponsor their marathon feat.
Childhood First is the fundraising arm of the Peper Harow Foundation.