Hello Dave,
John Mellard, son of Samuel, was buried 17/3/1859 age 12. I think the one you're looking for is John Fieldend Mellard born Denby Dale about 1846. The family is named Mellor in the 1851 and 1861 census records but the father William is later named Mellard in the 1881 census. William was christened at Greasbrough but probably born at Nether Haugh, the family moved to West Melton before he was 3 years old. The christening record (4/2/1810) shows William son of Samuel Mellors and Ann. Samuel Mellard and Ann Burgin were married at Rotherham church (only chistenings at Greasbrough) on 25/8/1806. This Samuel is the father of the one you mentioned. There are many different spellings in the christening records i.e. Mellard, Mellars, Mellar, Mellers, Mellor, Mellors.
Samuel is the son of William Mellard and Sarah Norton married at Wath on 22/11/1773.
1851 census> Denby> District 3c> record # 12
1861 census> Denby> District 6> record # 182
Regards,
John