My gx4 grandfather Luke Foster was born in 1858, the son of JOSEPH FOSTER & Susana Lenon. This is the first of two appearances of Joseph, the other one being his year of death being 1781 as recorded on Susana's burial record: "Buried Mrs Susanna Foster relict of Joseph Foster (dec 1781) and sister to the late TB Lenon (dec 1798)." I can find no further information on Joseph. (Susana's mother was Elinor Bunbury.)
There's been a story in my family, begun by Edward Bunbury Foster (Luke & Susana's son, my gx3 grandfather) that composer Stephen Collins Foster was a cousin. If that was the case, Joseph must've been related to Rev Alexander Foster, born about 1710 in Londonderry. Family folklore. I've not been able to find a connection. I've searched too many databases to name but including Ancestry, FMP, FamilySearch, irishgenealogy.ie, etc. The mystery as to who Joseph's forebears were remains just that!