Catherine Harrower married Duncan Morton Harrower 28th April 1950

Looking for info on Catherine Harrower nee Mullen. Catherine had a son to Duncan Morton Harrower,son Dennis was born 9th April 1950 and married Duncan on 28th April 1950. What I am wondering is what happen to her daughters from her previous marriage to Philip Cunningham? Daughters Anne born 8th March 1939 and Patricia 4th Feb 1948? Dennis is my stepdad and he never knew his half sisters.Catherine died when he was four years old. Any info would be greatly appreciated.