I found 2 baptism records on
www.familysearch.orgEliza Jane St. Clair 11 December 1864,
Cork,
Cork, Ireland
Mary Teresa St. Clair 26 February 1866,
Cork,
Cork, Ireland
Parents: William St. Clair and Mary Ann
Malone.
I, also, am looking for a St. Clair family from Co. Cork, Ireland. I believe the husband's name was Martin St. Clair and his wife was Ellen. Ellen is recorded on the 1881
Surrey,
England Census, Widow, 50, born Co. Cork, living with her married daughter Mary Jane (St. Clair)
Mahoney.
I wonder if these 2 families are related? Especially since you have William's father as "Martin".
Look forward hearing from you.