St. Louise de Marillac (1591 - 1660), a contemporary of St. Vincent, was inspired and directed by Vincent's spiritual leadership. She was Vincent's collaborator in founding the Daughters of Charity and organizing hospitals for the sick poor, asylums for the orphaned, workshops for the unemployed, championing literacy for the uneducated, and establishing standards for local charities. Louise was a wife, mother, teacher, nurse, social worker and religious foundress.

Sister Rosalie Rendu, a Daughter of Charity, is considered a mentor of Frederic and of the Society of St. Vincent de Paul as she taught the first members the art of helping the poor and the sick.  Sister Rosalie was very influential with the students who wanted to respond to the needs of the poor in their midst and bring about a more just society.  Frédéric dreamed of 'encircling the world in a network of charity'.  Sr. Rosalie taught the group of students how to make home visits to the poor.  Sister Rosalie helped the students learn to see Our Lord in the poor.  Giving the students families to visit, Sister Rosalie would give them advice on the Christian way to go to them, to respect them, and to consider them brothers and sisters, rich in humanness.  The mentoring provided by Sister Rosalie coupled with Frederic's own desire to be of service because the need was so obvious became the foundation for many of Frederic's writings on social justice.