What looks as though it might be the marriage between Wm Todd and Mary Anderson was registered in Banbridge 1847 Vol 2 page 397. (Indexes to Irish civil registration). The marriage cert should also be on-line on the GRONI site in Belfast but I can’t find it. So may just need to order a copy from GRO Roscommon.
You can order a photocopy of the certificate from GRO Roscommon for €4 (euros). http://www.welfare.ie/en/Pages/Apply-for-Certificates.aspx
You have to download and print off the form. Then either post or fax it back to them. You can’t e-mail it to them. However if you want them to e-mail the cert to back to you, they will do that, so tick the relevant box.
Put the reference details on the form (anywhere). Don’t worry about leaving some boxes blank. As long as GRO have the location, name(s), year, quarter (where there is one), volume and page number they should find it.
Tradition was to marry in the bride’s church which should be on the certificate, (unless it was a Registry Office marriage). That church may be the place to look for her baptism and that of any siblings.
Cappagh is a townland of 476 acres in the parish of Annaclone, near Banbridge. There’s a William Todd listed there in Griffiths Valuation of 1863. He was on plot 20 which was a 26 acre farm. That’s on the modern Burnside Rd. The revaluation records show the farm passing from William Todd to Andrew Todd in 1902 though those dates can be out by a year or two. William probably died around 1900 or 1901. (Possible death on GRONI on 14.2.1900 aged 83).
https://geni.nidirect.gov.uk
John & Samuel Todd lived nearby and so are probably related.
http://www.askaboutireland.ie/griffith-valuation/index.xml
1901 census:
http://www.census.nationalarchives.ie/pages/1901/Down/Annaclone/Cappagh/1207340/
1911:
http://www.census.nationalarchives.ie/pages/1911/Down/Annaclone/Cappagh/208798/
http://www.census.nationalarchives.ie/pages/1911/Down/Annaclone/Cappagh…
Andrew Todd is still shown as the owner of the farm in 1929 when that series of records stops.
You might find further information in PRONI, eg they have this holding: D2426/37
One of two boxes of miscellaneous title deeds, leases, conveyances, sale particulars, etc, including a coloured survey of Cappagh, Co. Down, by Alexander Richmond, 1838, and certified copies of 1851 census particulars of the Gray family of Ballynewport, Co. Down.