Seeking my grandfathers family

I searched for marriages in the Strangford area and found this one. Given the occupation shown, I suspect it may be connected to your family:

https://civilrecords.irishgenealogy.ie/churchrecords/images/marriage_returns/marriages_1852/09428/5415601.pdf

John Sweetman (Chief Boatman Coastguard in Strangford) son of James Sweetman, Mariner. Married in 1852. Given that your ancestor also became a mariner, and was born 3 years later, I suspect this may be his parents. What’s his father’s name and occupation according to the 1899 English marriage certificate?

Birth registration didn’t start in Ireland till 1864, so you would need to search church baptism records for his birth. This is possibly a mixed marriage since they married in a Registry office and also in church, so I would search both the Church of Ireland and RC records. Ballyculter Church of Ireland parish baptism records start in 1777. There’s a copy in PRONI (the public record office) in Belfast. (Personal visit required). Some years are on the rootsireland site (subscription). The RC  records (parish of Ball) start in 1844 and are on rootsireland and the national library of Ireland site.  Suspect the children were all brought up RC in this case so I’d start with the RC baptism records.

A mention of the Sweetmans owning a hotel in Strangford, and other properties, in 1901:

https://freepages.rootsweb.com/~rosdavies/genealogy/SURNAMES/S/StuSy.htm

Suspect this is John Patrick Sweetman’s widow and children in the 1901 census:

http://www.census.nationalarchives.ie/pages/1901/Down/Strangford/Strangford/1233227/

Note that some were born in Co Clare, and a grandchild in Wales. That fits with Coastguard service as they got moved around the country a lot.

The Coastguards of yesteryear website mentions a Luke Sweetman serving at Ballygeary (Co Wexford) in 1865. Perhaps a relation? The site also mentions Chief Boatman Mr Sweetman dealing with a wreck in Wicklow in 1867.

https://coastguardsofyesteryear.org/search.php?stext=Sweetman&search=Search&method=OR&forum_id=0&stype=all&datelimit=0&fields=2&sort=datestamp&order=0&chars=50

John Sweetman’s death in Strangford in 1896.

https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1896/05910/4677499.pdf

The Irish Weekly and Ulster Examiner of 15th Feb 1896 mentions his death, burial in Kilclief cemetery and a has  list of mourners. Item is attached.

Family in 1911:

http://www.census.nationalarchives.ie/pages/1911/Down/Strangford/Strangford_Lower/242459/

A probate abstract, from the PRONI wills site that is probably for one of John Patrick Sweetman’s sons:

Sweetman John P. of Strangford county Down draper died 4 November 1944 Probate Belfast 3 August to Joseph Fitsimons farmer. Effects £2840 9s. 4d.

The will itself should be in PRONI in paper format (ie not on-line). You can go there and view it free or pay PRONI to copy it for you.