Hi
Anne Williams (13/03/1803) and William Williams (1807) were children of William Samuel, NOT Samuel Williams, and Elizabeth his wife, Of Bryn Hafod Bach, parish of Clynnog. Under the Welsh system the children had 'surname' Williams. There is a burial, 14/08/1810, Owen son of William Samuel of Bryn Hafod Bach, an infant. A baptism, 09/06/1805, John son of William Samuel of Bryn Hafod Bach and Elizabeth his wife. A burial 24/11/1813, William Samuel of Bryn Hafod Bach age 63.
1861 Census, Bridge St., Llangefni, Anglesey, you have:
Anne Jones Widow 59 Pauper Carnarvonshire, Clynnog;
Elizabeth Jones daughter Unmarried 19 Servant Carnarvonshire, Llanllyfni;
William Jones son unmarried 17 labourer Carnarvonshire, Llanllyfni.
Been unable to trace family in 1841 and 1851 Censuses. There is an Elizabeth Jones aged 9 in 1851 Census, Llanllyfni, grand daughter, born Llanllyfni.
Perhaps Llanllyfni Parish Records will provide info, if they remained Church members rather than turned Nonconformists.
Emyr