Kevin/ Keiran Cummins

[Evandarcy]

Hello, my 5th great grandfather's name was Kevin/Keiran Cummins born from 1785-1800, he was either born in Dublin, Ireland or Scotland. The only record I could find of him was on his daughter (My 4th Great Grandmother) Mary Teresa Cummins marriage certificate to John Arthur on the 19th of Sep 1847. It lists his occupation as a soilder and thats why Im interested to learn more. I cannot seem to find any birth or marriage certificates for him. What websites can I use to research him further?

[aghadowey]

Civil registration in Ireland didn't start until 1864 (for all births, marriages, deaths except non-Catholic marriages which began in 1845). Therefore, there won't be a birth or marriage registration for him. Pre-1800s is also very early for church records in Ireland. Many Catholic parish registers are online (free) but coverage varies from parish to parish.
https://registers.nli.ie/ (since you don't even know a county it will be difficult to find details easily)
Have you tried tracing his children to see if they give more details about the family or done DNA testing?