He married Elizabeth Malinda Rogers, daughter of the late Benjamin, on 19 Mar 1866. 
In 1881, Robert and Malinda had children Maggie, Louis, Maud, Howard, Lutie, David, and Clara. 
Maggie married John A. Cameron; she died in Cambridge, Mass. in 1899. 
In the 1891 census in Lot 12: Robert, Malinda, Louis (21), Maud (20), Howard (18), Lutie M (17), David R [Rogers] (13), Clara (11) and [Irene] Mercedes (8).
When Robert died in 1917 , he was survived by his wife, three sons and four daughters: Louis, a contractor and builder in Seattle; [William] Howard, lathing contractor in Cambridge MA; David of Cambridge, MA; Maude, wife of Permenis [Parmenas] Moreshead of Malden; Mildred Helen (Lutie), wife of J. J. Macdonald of Boston; Clara, wife of Robert Hardy of Montrose and Irene, w/o Johnson Haywood of Elmsdale.
Three brothers also survive him: John Ellis of Northam; Penrose of Port Hill and Edward of Ellerslie.
Clara Hardy gave his date of death as October 30, 1919 in an "In Memoriam" insert in the newspaper in 1922.
On the baptismal records in Port Hill for their children, Robert Douglas was a ship and house carpenter.
↑ Along the North Shore, by J. Clinton Morrison, page 405
↑ Photo of gravestone, Find A Grave Memorial# 112168004
↑ Prince Edward Island Marriage Registers, 1832-1888," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:QVBJ-245L : 11 March 2015), Robt D Ellis and Elizb M Rogers, 19 Mar 1866; citing , Prince Edward Island, Canada, Public Archives, Charlottetown; FHL microfilm 1,630,093.
↑ Canada Census, 1881," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:MVN7-CG2 : 30 June 2017), Malinda Ellis in household of Robert D. Ellis, Lot 11, Prince, Prince Edward Island, Canada; citing p. 25; Library and Archives Canada film number C-13162, Library and Archives Canada, Ottawa, Ontario; FHL microfilm 1,375,798.
↑ Mass. Deaths and Burials, Cambridge Chronicle, 14 January 1899
It may be possible to confirm family relationships with Robert by comparing test results with other carriers of his Y-chromosome or his mother's mitochondrial DNA.
However, there are no known yDNA or mtDNA test-takers in his direct paternal or maternal line.
It is likely that these autosomal DNA test-takers will share DNA with Robert: