Thomas Jefferson Cooper married Mary Ellen Washburn who was born on March 20, 1839 and died on February 16, 1880 and was buried in and was buried in Oak Park, Illinois. They were married in 1858 in Red Wing, Minnesota.

Thomas and Mary Ellen had two children.  

1. Charles L. Cooper who was born in 1858. 

2. Julia Cooper was born about 1860.

After Mary Ellen Washburn died, Thomas J. married Mary Ellen's younger sister, Lucy Emma Washburn.  Lucy Emma Washburn was born on November 20, 1842 and died on March 20, 1915 in Fruita, Colorado.  Their marriage was in 1885 in Red Wing, Minnesota.  Thomas and Mary Ellen did not have any children.

Julia Cooper, daughter of Thomas J. Cooper and Mary Ellen Washburn, married Wallace A. Merriell on September 1, 1883. 

Mary Ellen Washburn and Lucy Emma Washburn had a younger brother named Millard Fillmore Washburn.  He was born on April 25, 1848 and died on July 4, 1921 in Cooperstown, North Dakota.  Millard married Mary Husel.

Note that Millard Fillmore Washburn married Mary Husel and his nephew, Charles L. Cooper married Laura Husel.  I'm not sure how or if Mary Husel and Laura Husel were related.

Millard Fillmore Washburn died of a stroke in his car near Mose, North Dakota on July 4 (14?), 1921.

Click here to see the Washburn genealogy going back to the Mayflower and beyond to about 1250 AD. 

Sources:

1. The Wight Family Genealogy

2. Compendium history and biography of North Dakota; a history of early settlement, political history, ... and biography; reminiscences of pioneer life ... (page 49)