Robert Winthrop, Jr. was born 7 December 1834 in Boston, Suffolk County, Massachusetts, United States to Robert Charles Winthrop (1809-1894) and Elizabeth Cabot Blanchard (1809-1842) and died 5 June 1905 Boston, Suffolk County, Massachusetts, United States of unspecified causes. He married Frances Pickering Adams (1836-1860) 1857 in Boston, Suffolk County, Massachusetts, United States.
Children
| Name | Birth | Death | Joined with |
| Robert Mason Winthrop (1873-1938) | |||
| Clara Bowdoin Winthrop (1876-1969) | |||
| Margaret Tyndal Winthrop (1880-1970) | 23 February 1880 Massachusetts | 7 July 1970 St.-Briac-sur-Mer, Brittany, France | James Grant Forbes (1879-1955) |
Residences
Footnotes (including sources)