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Having looked again at the 1841 entry, I see that there was indeed a Thomas:

1841
St Bees, Whitehaven

Ancestry’s transcription:

Name Age
Robert Cubbon 45
Robt Cubbon 7
Elizabeth Cubbon 45
Catherine Cubbon 20
William Cubbon 18
Thos Cubbon 16
Mary Cubbon 14
Bridget Cubbon 10
James Cubbon 2

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