Thanks dathai, your interest is much appreciated.
Yes, that 1901 census return is damaged but the forenames are just readable if you squint a bit. The ages don't 'quite' match for the girls but I thought it likely as the other person linked to that address on the Form B matches wth her son Francis, his wife and baby (their FormA also damaged but partly readable).
I do have Marion's marriage, birth and death of her only child and her death in 1907 (her widower remarried in 1913)
Mary snr's reported ages on various records seem to be arbitary to say the least. Full age, in 1866 when she married, 48 in 1901 on that census, 50 in 1904 when admitted to the workhouse hospital, 50 in 1905 when again admitted to the hospital and died there and, miraculously, 46 two days later when the workhouse registered her death. I feel that the 'full age' in 1866 would be nearest (if not quite accurate) to the truth as if she had been 46 when she died that would mean she was married at the age of 7 and was 8 when she had her first child:-)
The documents that I have for her are here:
http://www.rootschat.com/links/01lww/Her surname on childrens birth/death registrations is sometimes O'Kelly, sometimes Kelly.
Her parents were, according to the parish marriage record, Bartholomew Canning O'Kelly (a dealer according to the civil cert) and his wife Mary and a Kate Canning/Cannon O'Kelly was both a godmother and the registrant for a couple of the childrens births so may have been a sister or sister in law.
EDIT : She seems to have been Mary's sister, Catherine Cannon Kelly (a minor) married John Murphy 12 Oct 1873, St Paul Arran Quay, church record says Father Bartholomew Canon Kelly, deceasedSo far I am failing to find a baptism for Mary to try to find her actual year of birth.
The only two children I haven't yet sussed properly are Elizabeth Christina (born 1873, no records found so far after her birth registration) and Mary Esther (born 1883, no records found so far after the 1901 census).
I'll keep plodding on with it, something may turn up!
Boo