John was born in Alton, Staffs, and according to the 1851 census, Mary was born in Tatenhill, near Burton-on-Trent, Staffordshire.

With Mary being recorded as 43 in 1841 and 55 in 1851 several possible records for Mary's baptism are ..
  - at Leek, Jan 1798 (parents John/Elizabeth)
  - at Mapleton, July 1799 (parents James/Sarah)
Mary spent her early married life around Ashbourne, Derbyshire (William, Martha & Mary Udall were all baptised at Bradley, and Charles Forester at Osmaston), so my thoughts are that James & Sarah are more likely to be Mary's parents, Mapleton being only about 2 km from Ashbourne.

John and Dorothy were both born at Alton, where they married. They both died at Cheadle.

James was born at Blore and Sarah at Ashbourne. They married at Mayfield.