Hi again, Colette,
I rechecked the birth registration for sister Kathleen - it's a photocopy e-mailed to me and not too clear. But the address is written in three different columns and each time reads "6 Harold's Cross". The top of the document reads "District of Rathmines in the Union of Dublin South". Her father was a laborer and may have moved to find work. The first column (cert #?) is cut off. but the rest is legible. On both the ship manifests (Margaret's in 1917 and Kathleen's in 1920) their father is listed as Michael Lennox at "8 Bank Side, Milltown, Co.Dublin". Is it possible that the street names have changed over the years as the city expanded and took in these neighborhoods?
Thanks again for your help,