Many thanks PB, after searching for so long, it’s a wonderful feeling to have some answers
Following on from the 1851-2 census I was curious about the other absent son Theophile-Jean who was understood to be in Boston. It seems Theophile lived the remainder of his life in the USA, where he was known as John T Bureau.
https://www.familysearch.org/tree/pedigree/fanchart/KLCJ-H11In the 1900 USA census Theophile/John is living with his son George-Henri & family in Manistee, Michigan, a few years later he passed away 12 January 1903 aged 76. Theophiles’ wife Luce (same name as his mother) passed away a few years previously in 1900 aged 70
I was thrilled to stumble upon this delightful photo of George-Henri & his wife Georgina.
https://www.familysearch.org/tree/person/memories/9DDZ-FGM