His father, Michael Morris Healy (1796–1850), was a native of County Roscommon, Ireland who became a wealthy cotton planter after settling in Georgia.

Michael was unable to directly free his wife and children as manumission required an act of the Georgia General Assembly in exceptional circumstances.

[6] In February 2024, Washington Post writer Bryan Greene established through DNA evidence that the Healy siblings were blood relatives of abolitionist Ellen Craft, likely first cousins based on historical accounts.

In 1848, Craft escaped slavery in Macon, Georgia, not far from the Healys' birthplace, disguising herself as a white man traveling with her enslaved attendant, her actual husband.

"[1] Some three decades after the last of the Healy children died, Jesuit sociologist Albert S. Foley published a book in 1954 that detailed their biracial background.

[2] After Michael Healy became acquainted with Bishop John Fitzpatrick of Boston, he sent his son to the College of the Holy Cross, a newly founded Jesuit school in Worcester, Massachusetts.

"[5] He and his brothers Hugh, Patrick, and Sherwood were baptized at Holy Cross in November 1844, alongside the sons of Catholic convert Orestes Brownson.

Knowing there were rumors about his heritage in Boston, he expressed his apprehension about serving there to a confidante: "The mercy of God has placed a poor outcast on a throne of glory that ill becomes him.

[11] This was followed by appointments as personal secretary to Bishop Fitzpatrick (December 1854) and chancellor of the diocese (June 1855),[11] which gave him a significant role in diocesan affairs.

[3] During the American Civil War, Healy supported the Union, but was opposed to the Radical Republicans' plans for Reconstruction, believing it would lead to "the super-elevation of the negro.

[14] In March 1866, the new Bishop John Williams named Healy as pastor of St. James Parish, the largest Catholic congregation in Boston.

[3] In that position, he helped found the House of the Good Shepherd for homeless girls and successfully lobbied against legislation in the Massachusetts General Court to tax Catholic churches.

[2] However, Healy withdrew his prohibition after Leo XIII issued Rerum novarum in 1891 and endorsed the right of workers to form labor unions.

[2] Healy participated in the third Plenary Council of Baltimore from November to December 1884, and was appointed to serve on the Commission for the Catholic Missions among the Colored People and the Indians.

"[2] Healy celebrated his silver jubilee as a bishop in June 1900 and was given the honorary title of assistant to the papal throne by Leo XIII on that occasion.