Hello Laurap
In 1841 their is two households of the name Francis at Dedham.......the theory being that Robert Francis married Harriett in her home town which is not in Essex.........had 4 children and then moved back to Dedham to be near Robert's mum!
Now you need to find this family in 1851 and 1861 and then follow the children ........ hopefully this will lead to your John Francis
1841
PARNEY HEATH, DEDHAM
ROBERT FRANCIS 30 CARPENTER Y
HARRIETT " 30 N
SARAH " 8 N
WILLIAM " 6 N
HARRIETT " 4 N
ROBERT " 2 N
EDWARD " 9 MONTHS Y
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1841
MOHER CORNER, DEDHAM
SUSAN FRANCIS 75 Y
WILLIAM " 30 Y
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*and if you can make out the witnesses names at that marriage it might help
Regards
Bryant