Think you'll find that Keynsham (itself in Somerset) Registration District covers parts of both Somerset and Gloucestershire.
The family in 1891 are in Glastonbury:
Reference RG12, Piece 1915, Folio 48, Page 21
Wood House, Street Road, Glastonbury
Ruddle, John Albert  Head  M  31  Millers Carter 
Ruddle, Ann  Wife  F  36
Ruddle, Arthur J  Son  M  9  Scholar
Ruddle, Rachel A  Daughter  F  8  Scholar
Ruddle, Grace  Daughter  F  7  Scholar
Ruddle, Louise  Daughter  F  5  Scholar
Ruddle, Tom  Son  M  4  Scholar
Ruddle, Selina  Daughter  F  3
Ruddle, George W  Son  M  5 months
All born Keynshan, Somerset except the last child George, born Glastonbury