Hi,
I had a try searching for her on the 1901 census gov site for you , and like you I can't get anything either. I tried searching by first name only, cleo, Cleopatra, clia, Clea. Where born I put glamorgan, glamorganshire.
You've probably done this too, and thought of looking at the occupants of the house address where she was born. I tried an address search on the 1901 census, but nothing is coming up for Bishop ( or Bishops) cardiff, so that street may not be still there today
These are lists I'm getting back for Marchant , keyword glamorgan ( female):
Annie Marchant 2 Glamorgan Neath
Annie Marchant 36 Glamorgan Cardiff Glamorganshire Roath
Doris Marchant 4 Glamorgan Pontypridd Glamorgan Pontypridd
Dorothy Marchant 17 Glamorgan Pontypridd Bedford Bedford St Paul
Glaydis Marchant 1 Glamorgan Cardiff Glamorganshire Roath
Jessie Marchant 8 Glamorgan Pontypridd Glamorgan Pontypridd
Lucy Marchant 28 Glamorgan Pontypridd Glamorgan Pontypridd
Mabel Marchant 7M Glamorgan Cardiff Glamorganshire Canton
Maria Marchant 78 Glamorgan Llandaff Glamorgan Aberdare
Mary Marchant 6 Glamorgan Aberdare Glamorgan Aberdare
males:
Age Where
Born Administrative
County Civil Parish Occupation
Arthur Marchant 9 Glamorgan Cardiff Glamorganshire Roath School Boy
George Marchant 7 Glamorgan Pontypridd Glamorgan Pontypridd
Hubert Marchant 3 Glamorgan Cardiff Glamorganshire St John The Baptist
James Marchant 26 Glamorgan Caerphilly Glamorganshire Radyr Gardener Domestic
John Marchant 5 Glamorgan Cardiff Glamorganshire Roath School Boy
Llewellyn Marchant 52 Glamorgan Llandaff Glamorgan Aberdare Coal Miner
Mark Marchant 12 Glamorgan Cadoxton Glamorganshire Roath School Boy
Mark Marchant 45 Glamorgan Cardiff Glamorganshire Roath Labourer Dock
Sidney Marchant 50 Glamorgan Cardiff Devon Dawlish West Cattleman On Farm
Walter Marchant 3 Glamorgan Cardiff Glamorganshire Canton
I tried merchant as well, but nothing seems to be matching up. I couldn't search on just the name Marchant , and no Christian name , and no place of birth, as there were too many results error
Do you know if Cleopatra had any sisters or brothers? you could try searching for them ( or by her parents names) in 1901 . If she has ,what are they names and ages ? what are her parents names according to her birth cert?
Have you found her parents , or any older siblings ( if you know of any of her siblings and they are older than cleo/clia) in the 1891 census?
Maybe finding her parents , or if you know of any older siblings first of all in the 1891 census ( before Cleopatra was born ) may help you to find them in 1901, if you haven't found them already that is in 1891. I'm probably just suggesting all the things that you have may have done to try and find her.

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