LDS Pilot Site lists the marriage of Robert Gordon, age 27, son of Thomas Gordon, to Elizabeth Brodie, age 22, daughter of John Brodie, on 8 May 1857 Lackagh, Co. Kildare. The marriage is listed in civil registration index: 1857 Athy registration district volume 1 page 516- which means it was a non-Catholic ceremony (Protestant church or Registry Office) since registration of Catholic marriages began in 1864. The actual certificate will list their residences at the time of the marriage as well as Robert's occupation, place of marriage and names of 2 witnesses.
To connect Sarah Ada Gordon to the above couple, or any other family, you'll need to search for any existing baptism records since registration of births also started in 1864. However, early records often just list father's name.