Hi Victoria
John Kelly Westport birth 1876 drawing a blank.
Taking a John born 1876 to a Thomas with sisters Catherine and Anna/Anne as absolutes the LDS site turns up :-
John birth December 11 1876
Catherine birth May 10 1875
Anne Birth December 4 1873
Parents Thomas Kelly and Mary Meehan.
No other births attributed,though others may have occured without parents details being transcribed.
Place of Birth Lisballaly,Gurteen,Sligo.
A Thomas Kelly appears in the Griff Valuations Barony:Coolavin,Union:Boyle,Parish:Kilfree,Townland:Lisbaleely. Landlord:Lord De Freyne.
With all the upheavals in the late 19th C many families gravitated to the larger towns which may be a possibility here as no 1901 census details are evident for this family.
Hope the above may be of some help.