Okay, in the 1910 census apparently the other son's name is really JUSTINE, not JUSTIN.

1900 census:

Colorado > Saguache > Crestone > District 115

W. A. Bangs born Oct. 1861, married 13 years, born KY (father born ?, mother born PA)

Louise Bangs, wife, born Sept. 1867, mother of 2, 2 still living, born Utah (father born MO, mother born OH)

Lynn Bangs, daughter, born Jan. 1888, born Utah

Justine Bangs, son, born Dec. 1897, born CO

William's listed as a hack driver.