Linda,
There are copies of Ahoghill 1sts baptism and marriages in PRONI (the public record office) in Belfast. Baptisms and marriages both start in 1841. (The church was there long before that but no records have survived). Marriages from 1845 onwards are also on the GRONI website.
Ahoghill 2nd Presbyterian have baptisms from 1835 and marriages from 1836. Ahoghill 3rd baptisms from 1859 and marriages from 1845.
The above baptisms and pre 1845 marriages are not on-line. You need to go to PRONI in person or get a researcher to do that, in order to view them. Presbyterians generally didn’t keep death or burial records and there are none for those 3 churches.
Tradition was to marry in the bride’s church, after which she would attend her husband’s (unless of course they both happened to attend the same church) so often the marriage and subsequent children’s baptisms are not in the same church. So Ahoghill 1st is probably the Agnew family church but it may not be the Thompson’s.
If you haven’t found the Weir-Thompson marriage in the statutory marriage records which start on 1st April 1845 and are on-line then you can probably assume it was before that date.
Don’t expect too much from a pre 1845 marriage entry. Sometimes you don’t get a lot more than the date, the couples names and their 2 witnesses. Sometimes a townland or occupation but not always. Rarely parents names.
I noted this grave in Ahoghill 3rd (Brookside):
Erected by David Thompson, Greenock In memory of his daughter Elizabeth Thompson Who died at Ballylummin 20th May 1891 aged 14 years Also his beloved wife Betty Thompson Who died at Greenock 1st June 1900 aged 54 years Also the above named David Thompson Died at Greenock 14th April 1929 aged 84 years Also his daughter Agnes Thompson Who died 6th Jan 1948 aged 78 years 'Asleep in Jesus'
Scottish death certificates contain both parents names, so if you are interested in the above family, you might get a bit more information about them from those certificates. You can view them in the Scotlandspeople site for about £1.60 each (sterling).
And:
Erected In memory of Joseph Thompson of Ballylummin who departed this life 15th of January 1846 aged 68 years Also his son Samuel depd this life 17th Septr 1899 aged 77 years And his wife Eliza Thompson died 29th Dec 1915 aged 88 years
I see just 2 Thompson farms in Ballylummin in Griffiths in 1862. They were beside each other and so are probably related (Thomas and Samuel senior). So the above graves may be related to your family.
There are many Agnew & Thompson graves in all 3 Presbyterian churches, and in the Church of Ireland and in the Old graveyard.
You didn’t say whether the Agnew family are also from Ballylummin but if they are, there’s gravestones in both the 2nd & 3rd church graveyards.
Both Thompson and Agnew are of course common Scottish surnames and Ahoghill was very heavily settled by Scots in the 1600s. The area is awash with both surnames.