Hi, well as to where they lived, I found the following baptisms
Moses, born the 3rd day of Aug. 1847
Robert born the 3rd day of Jan. 1850
Mary Ann born the 3rd day of March 1852
children of Robert Marshall,farmer, township of Nelson, and Mary, his wife, her maiden name Aidthorpe, were baptized the 19th day of March 1852.
ST. PAUL'S CHURCH, QUEBEC
George, son of Robert Marshall of the parish of Quebec, sawyer and of Mary his wife by her maiden name Aisthorp, was born on the 1st day of Aug. and was baptized on the 24th of the same month in the year 1845.
**so the family was in Quebec by 1845
Emma, daughter of Robert Marshall and of Mary, by her maiden name Aisthorp, his wife, was born on the 13th day of Sept. 1855 and baptized on the 5th day of May 1856
I didn't find Henry's bapt. and the two younger were born ON before the birth records database starts.
You mention 7 children, Abigail, George, Moses, Robert, Mary Ann, Emma and Henry with Henry being the youngest, but the 1871 census has
Robert 52, Mary 52, Moses 24, Robert 21, Henry 15, William 13, Charlotte 8
all children born Quebec except last two Wm. and Charlotte born ON
son George is living next door to them , he is age 26
1861 has Robert 42, Mary 43, George 14, Moses 12, Robert 11, MaryAnn 9, Emma 9, Henry 5, William 3