Thanks Trish. No I've already ruled out that Susan and Mary. They are both children of Benjamin Charlton Cooper and Henrietta Francis Jackson although some BD&M records have her as Francis Henrietta. That Susan married Steven King and was having children with him when mine had left with her husband Lionel Edward Dyne Towner and moved to Qld. Definitely not the right ones.
The family of Benjamin Lancaster Cooper were quite notorious. Their first son William Lancaster Cooper was in and out of jail and finally married Rebecca Shannon the widow of the hung murderer Daniel Boon. In about 1856 Benjamin Lancaster Cooper was himslf tried for murder when he and two of his mates beat a man who died of his injuries. They only got off because they couldn't or wouldn't say who threw the fatal blow.
There are numerous police and court documents about the male members of the family but at some point a newspaper article refers to two of his daughters teaching Sunday school at a Church in Parramatta. Seems ironic doesn't it. At some point some of them start using the Cooper surname. Maybe because of the notoriety but I think they used it long before. There are marrige listings for Frances Hilliard for Benjamin Cooper Lancaster and for Benjamin Cooper in the same year and at the same church. I think my Susan Cooper maybe one of the daughters. She died in Qld in 1944 but nothing on hers. Mind you she was married to a Magistrate so I can understand that they didn't want to be connected. They didn't register Frances Hilliard's death. She died in 1885. Susan's marriage certificate says her parents were Benjamin Cooper and Francis but she's definietly not one of the other Benjamin's.