[1] His father, George Walter Sundborg (1913-2009), was a newspaper reporter and editor, and longtime assistant to Ernest Gruening when Governor and U.S.

George Sundborg was a delegate to the Alaska State Constitutional convention in 1955–56, where, as Chairman of the Committee on Style and Drafting, he was responsible for selecting most of the words in that document.

[3][2] Stephen Sundborg entered the Society of Jesus in 1961 and was ordained a Roman Catholic Jesuit priest in 1974 in Seattle.

[4] He taught theology at Seattle University from 1982 until 1990, when he was appointed the Provincial of the Northwest Jesuits, a position he held until 1996.

In October 2019, Seattle University removed references to Planned Parenthood as a student resource from its website, after anti-abortion group Students for Life of America sent a letter to Sundborg and other university leaders in August 2019 arguing that Planned Parenthood had "no place on a Christian campus" as an "abortion corporation".

[6] An excerpt from Sundberg's email response to the request to remove references to Planned Parenthood: Thank you for contacting me about this matter.

I made this decision, consistent with my own and other presidents’ previous practice, in my responsibility to publicly represent our university as Catholic and in reflecting the central teaching of the Catholic Church regarding abortion—specifically as a significant moral issue and not any other services provided by Planned Parenthood.

The decision I made was based on my policy as president that faculty and staff should have the personal and academic freedom to associate with Planned Parenthood but that the university and its offices and divisions will not formally endorse the organization.