Hi Shane,
Yes! The 1880 US Census lists my grandparents just as you've noted above. I've been able to locate Mary (widowed) with Nicholas as head of household twenty years later in the 1900 US Census. In 1900 they were living at 445 West 32nd Street in NYC (which is now where Penn Station is in NY, I believe). The household then was:
Nicholas, Head of Household, Single, DOB: July, 1876, Age 23, "Heavy Box Maker"
Mary, Widowed, Age 42 (her DOB year is different here than on 1880 census but does list her immigration as 1872)
Edward, Brother to Nicholas, Age 18, DOB: May (?) 1882, "Assistant Shipping (?) Labor (?)"
Mary, Sister to Nicholas, Age 16, DOB: January, 1884, "Cash Girl"
Julie*, Sister to Nicholas, Age 13, DOB: October, 1886, "At School"
Martin, Brother to Nicholas, Age 10, DOB: July, 1889
and Joseph O'Donnell, listed as a 'border', Age 29, DOB: October, 1871, "Clerk in a Paper Store"
NOTE: Nicholas' older sister, Catherine, is not listed on this Census and would have been 25 or 26 years old and on her own, I imagine.
*Julie is my grandmother, Julia Agnes Sinnott Coffinger.
It also lists Mary as having given birth to 10 children, only 6 of them living in 1900. I know of one son, Joseph Miles, who had died between 1887 and 1900. The youngest child, Martin Joseph, may have been named after his older brother who died.
Any help is great appreciated... I'm really at a road block, I feel
Thank you,
Jan