Here's how this family relates to Troy:
This first census is actually Troy's great-great Grandfather and his young wife and child in 1880. This was taken 4 months before Troy's great-grandfather was born, so Thirza (or Thersea) would have been pregnant at this point.
Source: 1880 U.S. Census, Kanosh Precinct, Millard, Utah, population schedule, Kanosh Precinct, Millard County, Utah, enumeration district (ED) ED 1, SD 33, 15, dwelling 133, family 133, Oscar A. Anderson Household; digital images, FamilySearch (familysearch.org : downloaded 5 February 2013).
Lines 15-18. Dwelling #133, Family #133.
Page 15, SD 1, ED 33
Kanosh Precinct, Millard County, Utah
7 June 1880
Line 15. Anderson, Oscar A, W, M, 25, Head, married, Freighter, POB: Denmark, Father POB: Sweden, Mother POB: Denmark.
Line 16. ---, Thirza J, W, F, 24, Wife, married, Keeping House, POB: Utah, Father POB: US, Mother POB: Tennessee.
Line 17. ---, Mary E, W, F, 1, Daughter, single, POB: Utah, Father POB: Denmark, Mother POB: Utah.
Line 18. Halsey, William A, W, M, 34, Boarder, single, Saddle & Harness Maker, cannot write, POB: N. Jersey, Father POB: New Jersey, Mother POB: New Jersey.