Mary was the sister of the "Waving Girl of Savannah". Their brother George took over job as lighthouse keeper in 1887 after the passing of their father, Sgt. John H. Martus. Sgt. Martus enlisted in the U.S. Army when he was only 14. It wasn't long before he met and married their mother, Rosanna Ceceilia Decker, (born October 31, 1831), of Philadelphia. At the close of the American Civil War (1866), Sgt. Martus was a disabled decorated war veteran who was appointed Ordnance Sergeant at Fort Pulaski, Georgia. This fort played a prominent role in the capture of Savannah during the Civil War. The Union forces of the North bombarded it with their naval forces and it was badly in need of repair. Sgt. Martus was sent to supervise weapons and the men assigned to rebuild the fort. He brought with him his pregnant wife and four children. (Annie, born in 1846 in Deleware; Charles F. born April 27, 1853 in Rhode Island--died Sep 23, 1876 at the age of 23; Rosanna, born in 1858 in Minnesota; George born May 31, 1861 in Washington D.C.--Mary Alfreta was born at Elba Island in 1866 and Florence, "The Waving Girl" was also born on Elba Island on August 7, 1868.) They were assigned to live in the cottage that faced the Savannah river. After the repairs were completed at Fort Pulaski, Sgt. Martus was assigned keeper of the lights at Elba and Cockspur Islands. Sgt Martus and his family resided there until August, 1881 when a category 3 hurricane destroyed their cottage. The family moved to Savannah and John passed away leaving son George and daughter Florence to tend the lights. George tended the light and cared for Florence, "The Waving Girl of Savannah" and his mother Cecilia until her passing in 1909. George retired in 1931 taking Florence to live with him in Bona Bella on the outskirts of Savannah. George and Florence were credited with saving a crew on a government dredge from drowing after it caught fire in 1885, and rescuing 30+ men from a sinking boat during the hurricane of 1893. George is buried next to Florence in Laurel Grove Cemetery in Savannah.

Mary married Thomas Brennan around 1891 and gave birth to six children; Mary, born in 1892; Thomas Aloysius Brennan born November 13, 1894 in Savannah and became a monsignor in the Catholic Church, he died October 27, 1963 and is buried at Blessed Sacrament Church in Savannah; John born in 1897; James born in 1899; Florence born in 1902; and Joseph born in 1905. Mary's husband Thomas was a policeman in Savannah until his death June 6, 1938.