He appears in the 1860 census in the same household as Mary Williams and a 1 year old boy, George M. Williams.  Next in this household are Teresa E. Harvey and 4 children of ages 6 years to 6 months.  There is no indication that he was married to either of these women, although he apparently started a family with Teresa in the early 1860s.  Mary and Teresa are said to have been sisters.

George is said to have fought in the Civil War, been captured, and held prisoner until February 14, 1865.

George M. Harter, Mary J. Williams and her 11 year old boy aren't found in the 1870 census.  However, "Therey Harvey" (age 45) with children Mary (age 18), William (age 16), Elizabeth (age 14), Amanda (age 12), Luther (age 10), Joseph (age 8), Jane (age 6) and Sarah (age 4) are listed in 1870.

However, George and Mary J. (and possibly their 21 year old son) re-appear in the 1880 census, 8 years after Teresa's death.  The 1880 census shows him with a wife named Mary (who apparently was Mary J. Williams) and 11 children.  The eldest child is "W.A", a son of age 21; this may have been the son of Mary Williams named as George M. Williams in the 1860 census; the other 10 children listed in 1880 were born after 1860.  The first 4 children of Teresa E. Harvey would have been in the 20-26 age range, and apparently had left the household by this time (3 daughters between ages 26-20) and a son age 24).

Speculation:
In 1860, George Harter had two women in his household, said to be sisters.  The younger sister, Mary Williams, had a 1 year old son, whose father is unknown (but possibly George Harter).  Older sister Teresa had 4 children, all surnamed Harvey.

George Harter first started a family with Teresa in the early 1860s; she then had 8 additional children between 1861 and 1872 (the year of her death).
After Teresa's death in 1872, he started a second family with Mary, who had two more children between 1873 and 1878.