I assume these are your Isaac and Ann:
1841 HO107/294/6
Holy Trinity, Dorchester
Isaac Miller, 50+, ag lab, Y
Ann Miller, 45+, Y
Eliza Miler, 20+, Y
John Miller, 15+, Y
Leah Miller, 14, Y
Jane Miller, 10, Y
Frederick Trevet, 2, Y
1851 HO107/1858
Tubs Corner, Fordington
Isaac Miller, 60, wid, ag lab, b Bradford, Dorset
Eliza Miller, unm, dau, 20, ag lab, b Fordington
Jane Miller, unm, dau, 19, b Fordington
Frederick Jas Miller, g-son, 2, b Fordington
Isaac Miller, son of Edward and Leah Miller, was baptised in 1793 in Bradford Peverell (on IGI; as are some of the children of Isaac and Ann).
Richard