The four births after 1837 show MMN = CUNLIFFE, but there is no corresponding marriage. This is easily explained if Mary had been married before.
30 March 1823, Mary Ann Cunliffe married James Bolton at Walton-le-Dale near Preston. James died in Dec 1823, just 9 months after he had married, aged 19.
2 Sep 1826, Mary Bolton (Wid) married Robert Mather at St Lawrence, Chorley.
In 1841, Robert and Mary (both 35) were at Pall Mall, Chorley with James (10), Ann (10), Richard (9), John (7), Thomas (4), Easther (6) and William (2)
In 1851, Robert and Mary (both 47) were at Pall Mall, Chorley with Richard (20), John (18), Esther (16), Thomas (14), William (12), Mary Jane (9), Robert (5) and Jane (2).