 Eustis was for many years a confirmed bachelor, described as urbane and charming. He married Caroline Langdon in 1801; they had no children. She was the sister of Henry Sherburne Langdon, who had married Eustis' sister Ann, and the daughter of Woodbury Langdon, a prominent Portsmouth, New Hampshire merchant and judge. His wife survived him by forty years, after which his Boston property was divided among relatives. The mansion fell into decay, but was acquired by preservationists in 1913 and restored to its 19th-century grandeur in the late 20th century. It is now a house museum and a National Historic Landmark.
