On November 2, 1887, Mack married Margaret Hogan, whom the Spencer Leader described as having "a sunny and vivacious disposition."
They had three children, Earle, Roy, and Marguerite.
Margaret died in December 1892 after complications from her third childbirth.

Mack married a second time on October 27, 1910.
His second wife was Catherine (or Katharine) Holahan (or Hoolahan) (1879–1966); the census records have various spellings (the wedding register reads "Catarina Hallahan").
The couple had four daughters and a son, Cornelius Jr. A faithful Catholic his entire life, Mack was also a longtime member of the Knights of Columbus (Santa Maria Council 263 in Germantown, which moved to Flourtown, Pennsylvania in the 1980s).

Mack's son Earle Mack played several games for the A's between 1910 and 1914, and also managed the team for parts of the 1937 and 1939 seasons when his father was too ill to do so.
In more recent years, his descendants have taken to politics: Mack's grandson Connie Mack III was a member of the U.S. House of Representatives from Florida (1983–89) and the United States Senate (1989–2001); and great-grandson Connie Mack IV served in the U.S. House of Representatives (2005–13), representing Florida's 14th congressional district.
On November 2, 1887, Mack married Margaret Hogan, whom the Spencer Leader described as having "a sunny and vivacious disposition." They had three children, Earle, Roy, and Marguerite. Margaret died in December 1892 after complications from her third childbirth.
Mack married a second time on October 27, 1910. His second wife was Catherine (or Katharine) Holahan (or Hoolahan) (1879–1966); the census records have various spellings (the wedding register reads "Catarina Hallahan"). The couple had four daughters and a son, Cornelius Jr. A faithful Catholic his entire life, Mack was also a longtime member of the Knights of Columbus (Santa Maria Council 263 in Germantown, which moved to Flourtown, Pennsylvania in the 1980s).
Mack's son Earle Mack played several games for the A's between 1910 and 1914, and also managed the team for parts of the 1937 and 1939 seasons when his father was too ill to do so. In more recent years, his descendants have taken to politics: Mack's grandson Connie Mack III was a member of the U.S. House of Representatives from Florida (1983–89) and the United States Senate (1989–2001); and great-grandson Connie Mack IV served in the U.S. House of Representatives (2005–13), representing Florida's 14th congressional district.
Connie Mack