ME...
The 1910 census for Worcester shows my friend's grandfather, James Durkin, 28 with wife Annie (Boyle) 28 and dau. Mary 1. Census indicates James arrived in US in 1900, Annie in 1898. 28 years old would put his birth at 1882, however as you say, these dates can be off for many reasons, including a less than attentive census-taker.
The James J. Durkin shown in the 1900 census, cousin to and living in the household of James J. Cawley on Harrison St., certainly fits a scenario of him arriving in US in 1900 and not having a household of his own yet. James's birth date is given as June 1877 and this fits with the information you found on Familysearch.
Next challenge is to backtrack his trail into Ireland and see what can be found. Of interest is that James J's paternal grandmother was a Bridget (Walsh) Durkin. No indication that she or her husband emigrated from Ireland.
Thanks again for your good help.
Tom