Lafferty and Sinnott families? Possibly Oylegate

[corinne]

Edward Sinnott death record (from familysearch)
New York, New York City Municipal Deaths
Name   Edward Sinnatt
Event Type   Death
Event Date   23 Jan 1897
Event Place   Manhattan, New York, New York, United States
Address   445 W 32 St
Residence Place   New York, New York, New York
Gender   Male
Age   40
Marital Status   Married
Race   White
Occupation   Bin Maker
Birth Year (Estimated)   1857
Birthplace   Ireland
Burial Date   25 Jan 1897
Burial Place   New York, New York, New York
Cemetery   Calvary
Father's Name   Edward Sinnatt
Father's Birthplace   Ireland
Mother's Name   Kate Sinnatt
Mother's Birthplace   Ireland

birth date doesn't seem to match census and other records, but I think the occupation is right.

[bostonjan]

Corinne! Thank you SO VERY MUCH! I hadn't seen this information with the parents listed previously on familysearch.org.  This is the first substantial lead I've had in years.  Bless you! : )

[Wexflyer]

Now that the Catholic registers are available, and indexed, have you tried searching?
Looking for an Edward Sinnott, son of Edward and Catherine, in the 1850s time frame, I see only one match

Name:   Edward Sinnott
Baptism Age:   0
Event Type:   Baptism
Birth Date:   1854
Baptism Date:   24 Jul 1854
Baptism Place:   St Andrew's, Dublin city, Dublin, Ireland
Parish Variants:   St. Andrew's, Westland Row, Westland Row
Diocese:   Dublin
Father:   Edward
Mother:   Catherine

Searching for a brother James provides the following record for an older brother.
Name:   James Sinnott
Baptism Age:   0
Event Type:   Baptism
Birth Date:   1851
Baptism Date:   5 Oct 1851
Baptism Place:   St Andrew's, Dublin city, Dublin, Ireland
Parish Variants:   St. Andrew's, Westland Row, Westland Row
Diocese:   Dublin
Father:   Edward
Mother:   Catherine

I think it is reasonably clear that these are a good match. James would be a tad young to enlist in 1864 (though, unfortunately, not unheard of), so I wonder if you ever established whether the James who joined up was related, or not.