George Stewart Scott married Margaret Charlotte Miller on 15 Oct 1868 at St. Thomas, Stepney, Middlesex, England.
Source: "England Marriages, 1538–1973 ," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:NJ8Y-C19 : 10 February 2018), George Stewart Scott and Margaret Charlotte Miller, 15 Oct 1868; citing St. Thomas, Stepney, Middlesex, England, reference vP93 p194 cn388, index based upon data collected by the Genealogical Society of Utah, Salt Lake City; FHL microfilm 597,935.
Here they are in the 1871 census:
Name George S Scott
Event Type Census
Event Date 1871
Event Place All Saints Poplar, London, Middlesex, England
Enumeration District 22
Marital Status Married
Relationship to Head of Household Head
Birth Year (Estimated) 1846
Birthplace Poplar, Middlesex
Entry Number 22
Affiliate Image Identifier GBC/1871/0584/0245
Household Role Sex Age Birthplace
George S Scott Head M 25 Poplar, Middlesex
Margaret C Scott Wife F 25 Poplar, Middlesex
Eliza L Scott Daughter F 1 Poplar, Middlesex
Agnes Millar Visitor F 14 Poplar, Middlesex
"England and Wales Census, 1871", database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:VB6C-DCY : 9 December 2017), George S Scott, 1871.
Birth record for their daughter to confirm this is the right couple:
SCOTT, ELIZA LOUISA MILLER
GRO Reference: 1870 M Quarter in POPLAR UNION Volume 01C Page 737