Elizabeth had at least three siblings
Mary Anne, born 20/9/1839
John, 13/6/1844
Raymond, 13/6/1844 (Twins).
Not that the godfather for Raymond (born 13/6/1844) is also Raymond Dowling - grandfather?
I suspect the marriage of Raymond Dowling and Mary Holbrook is recorded in the Wexford parish registers - perhaps someone with a direct connection might care to look.