Home of the family descended from Morgan Gwal y Ci who traced to Ideo Wyllt. 

William ap John (6th in descent from the said Morgan) lived at Ystradwrallt, and was the father of David Williams who succeeded to Ystradwrallt, and John Williams of Ffos Las. John married Anne daughter of George Bowen of Crugbychan, Verwig parish, Cardiganshire, and was followed at Ffos Las by his son John Williams who married Lettice daughter of Richard Lewis of Trefynys, Abergwili parish (Carmarthenshire).

John was living in the years 1657-1663, and owned a small estate, including the capital messuage of Allt y gog in Abergwili which he sold in 1658 to David Morgan, Esq.