I think Patrick Saul was a widower when he married Sarah. There is a Patrick ,widower, with 3 children in 1881 .
1871 has a Patrick 'Soul' with wife Mary A,2 sons and a daughter Mary ,8 months old. Patrick,Mary A and 2 sons born Ireland,Daughter born Liverpool.
Maybe one of these children was the parent of Dorothy.Maybe she gave her grandfathers name at her wedding!
1871 Source Citation
Class: RG10; Piece: 3762; Folio: 109; Page: 22; GSU roll: 841880
1881 Source Citation
Class: RG11; Piece: 3603; Folio: 92; Page: 8; GSU roll: 1341863
There is also a death in 1880 for Mary A Soul.
Burial Record (Address Boundary St, same as 1881 census for family.)
Name: Mary Ann Saul
Birth Year: abt 1845
Death Year: abt 1880
Burial Date: 24 Mar 1880
Parish: Ford Cemetery, Lancashire, England
Mary Ann Saul
Estimated Birth Year: abt 1845
Registration Year: 1880
Registration Quarter: Jan-Feb-Mar
Age at Death: 35
Registration district: Liverpool
Inferred County: Lancashire