Jemima Lewis was born in 1885 and registered in Jun q in Cleobury District.
So I think that confirms Robert's birth there in 1921.
In 1901 (I don't have access but using 1901 census online) she is shown as a 16 yr old, born Lubberland and living in Exeter. Occupation is 'Inmate.'
Hopefully someone with access can find out where she was living but I suggest a workhouse.
As I said I don't have access but this is all I can offer you:
1891 - Cleobury Mortimer
George LEWIS, 39
Emma LEWIS, 14
John LEWIS, 12
Rhoda LEWIS, 10
Thomas LEWIS, 8
Jemima LEWIS, 6
Edwin LEWIS, 3
The mother might be Sarah, 35.
My computer won't let be post posts of a certain size so I have to stop here!