Commenters had a range of reactions to the post, with some showing their support for the family and others questioning how practical one shared name could be.
“This is going to be a nightmare for medical and school records”, one wrote.
Heffernan told the Daily Mail she wasn’t fazed by the criticism as “the internet always has opinions”.
“Our family doesn’t need outside approval. The girls love their names, and that’s what matters.”
While relatives were “surprised” by the choice, Heffernan said it was based in family history, “not novelty”.
“Mary is a strong name. To me, it represents humility, steadiness and strength. It’s a name that has endured for generations, and I love what it stands for as a foundation for our family.
“I’m honoured to carry the name myself, and naming our first daughter Mary felt like a natural way to honour one of our grandmothers and continue that tradition.”
The family cattle brand, Five Marys, was also inspired by the unusual naming pattern.
Heffernan was emphatic that the shared name hadn’t held her daughters back.
“Each of them has a strong sense of self and very different personalities”, she said. “The shared name hasn’t defined them. If anything, it’s grounded them in family tradition.”
Each Mary goes by a nickname to differentiate between them – MaryFrances goes by the name Francie, MaryMarjorie goes by Maisie, MaryJane goes by JJ, and MaryTeresa goes by Tessa.
“It’s rarely confusing in everyday life … really only when we’re trying to clear TSA as a family“, she said.