Flexner had three brothers named Jacob, Bernard and Simon Flexner.
He also had a sister named Rachel Flexner.

The success of Abraham Flexner's experimental schooling allowed him to help finance Simon Flexner's medical education at Johns Hopkins School of Medicine.
He proceeded to become a pathologist, bacteriologist and a medical researcher employed by the Rockefeller Institute for Medical Research from 1901 to 1935.

Flexner also financed his sister's undergraduate studies at Bryn Mawr College.
Jacob ran a drugstore and used the profits from selling the establishment to attend medical school.
He then practiced as a physician in Louisville.
Bernard pursued a career in law and later practiced in both Chicago and New York.

In 1896, Flexner married a former student of his school, Anne Laziere Crawford.
She was a teacher who soon became a successful playwright and children's author.
The success of her play Mrs. Wiggs of the Cabbage Patch (based on the 1901 novel) funded Flexner's studies at Harvard and his year abroad at European universities.
The couple had two daughters Jean and Eleanor.
Jean went on to become one of the original employees of the United States Division of Labor Standards.
Eleanor Flexner became an independent scholar and pioneer of women's studies.

Flexner grew up in an Orthodox Jewish family, however, early on he became a religious agnostic.

In addition to contributions by his brother Simon, their nephew, Louis Barkhouse Flexner, was founding director of the Mahoney Institute of Neurological Sciences at the University of Pennsylvania and a former editor of the Proceedings of the National Academy of Sciences.
Flexner had three brothers named Jacob, Bernard and Simon Flexner. He also had a sister named Rachel Flexner.
The success of Abraham Flexner's experimental schooling allowed him to help finance Simon Flexner's medical education at Johns Hopkins School of Medicine. He proceeded to become a pathologist, bacteriologist and a medical researcher employed by the Rockefeller Institute for Medical Research from 1901 to 1935.
Flexner also financed his sister's undergraduate studies at Bryn Mawr College. Jacob ran a drugstore and used the profits from selling the establishment to attend medical school. He then practiced as a physician in Louisville. Bernard pursued a career in law and later practiced in both Chicago and New York.
In 1896, Flexner married a former student of his school, Anne Laziere Crawford. She was a teacher who soon became a successful playwright and children's author. The success of her play Mrs. Wiggs of the Cabbage Patch (based on the 1901 novel) funded Flexner's studies at Harvard and his year abroad at European universities. The couple had two daughters Jean and Eleanor. Jean went on to become one of the original employees of the United States Division of Labor Standards. Eleanor Flexner became an independent scholar and pioneer of women's studies.
Flexner grew up in an Orthodox Jewish family, however, early on he became a religious agnostic.
In addition to contributions by his brother Simon, their nephew, Louis Barkhouse Flexner, was founding director of the Mahoney Institute of Neurological Sciences at the University of Pennsylvania and a former editor of the Proceedings of the National Academy of Sciences.
Abraham Flexner