In 1857, Benjamin Brewster married as his first wife, Elizabeth von Myerbach de Reinfeldts, the widow of Dr. Shulte of Paris, France. Elizabeth died in 1868; however, Benjamin continued to spend many vacations with his wife’s parents in Germany near Cologne. He was remarried on July 12, 1870. His second wife, Mary Walker, was born in Mississippi on December 13, 1839, and died on March 9, 1886, in Philadelphia, Pennsylvania. She was the daughter of Robert John Walker, Secretary of the Treasury under President James Knox Polk and Mary Blechenden Bache. The latter Mary was the daughter of Sophia Durrell Dallas and Richard Bache, Jr., who served in the Republic of Texas Navy and was elected as a Representative to the Second Texas Legislature in 1847. Sophia, the daughter of Arabella Maria Smith and Alexander J. Dallas an American statesman who served as the U.S. Treasury Secretary under President James Madison. She was also great-granddaughter of Sarah Franklin Bache and Richard Bache, and the great-great-granddaughter of Benjamin Franklin, as well as niece of George Mifflin Dallas, the 11th Vice President of the United States, serving under James K. Polk. Mary Walker had married as her first husband, on May 25, 1858, Adrian Deslonde, the son of André Deslonde, a sugar planter from St. James Parish, Louisiana. His sister, Caroline Deslonde, married P.G.T. Beauregard, the Louisiana-born author, civil servant, politician, inventor, and the first prominent general for the Confederate States Army during the American Civil War. Through his sister, Mathilde, he was a brother-in-law of John Slidell, a U.S. senator from Louisiana and later a Confederate diplomat. John’s sister, Jane Slidell, was married to Matthew C. Perry, who was the Commodore of the U.S. Navy who compelled the opening of Japan to the West with the Convention of Kanagawa in 1854.

In 1846 Benjamin Brewster was appointed commissioner by President James K. Polk to adjudicate the claims of the Cherokee against the U.S. federal government. He was appointed Attorney General of Pennsylvania in 1867 by Governor John W. Geary. He was chief prosecutor in the case of the U.S. Postal Service’s Star Route Frauds. In 1881, Chester A. Arthur appointed Brewster Attorney General of the United States, an office he held for the duration of Arthur’s term. Benjamin Brewster died on April 4, 1888, at Philadelphia, Pennsylvania, where he is buried in Woodlands Cemetery.