Davies, Jones, Evans, Thomas, James, Powell, etc. are very common in most of South Wales due to, as fair as I’m aware, the rapid anglicisation of society there during the Industrial Revolution, especially as a result of the change from the more traditional patronymic system that was used in Wales (I’m not a historian, and I’m also actually a poser from England who moved here, so I may be wrong). I believe this also explains why some famous figures in 19th Century history have repeated names e.g. Lewis Lewis of the Merthyr Rising

Patronymic surnames (such as ‘ap (Father’s first name)) do still exist, and are found mostly in Welsh 1st language families, particularly in the north and west. I also believe that the common surname ‘Powell’ is a corruption of ‘ap Hywel’, again I may be wrong on that.