This is the 1880 census of 85 Luqueer St., showing the Madigan family (though it's spelled Maddigan). Matthew and Margaret both give their ages as 40, giving each an approximate birthdate of 1840. Both say they were born in Ireland, but all of their 3 children were born in NY. Margaret, at 7, has not yet attended school, but Mary, at 11, and James, at 9, both have. According to these ages, Mary was born around 1869, James around 1871, and Margaret around 1873. Matthew's occupation is "truckman," and Margaret is listed as "keeping house." Also listed with their family is 21-year-old Matthew Kelly, who must be a boarder, and who works as a "clerk in store."
What's even more interesting though is several lines further down the page. Also living at 85 Luqueer St., and also a "truckman" by trade, is Cornelius Sullivan, age 30, and his wife Margaret. If we look back to this information that we got from someone's cousin or something or other, we see that Margaret Sullivan Madigan had her siblings listed: Bridgett, Nora, Conn, and James. I have a suspicion - no proof, just a suspicion - that "Conn" is an abbreviation for Cornelius, and that this Cornelius Sullivan is Margaret's brother, working with his brother-in-law Matthew as a truckman. I haven't come across any evidence that Conn actually ever was used as an abbreviation for Cornelius, and Sullivan is a common name. Still, someone who shares a last name with Margaret and is working in her husband's industry while living in the building they own is just too tempting to write off entirely.