I know this is an old thread but the topic is still open. I have seen many people listing Thomas Ellis as the son of Rowland Ellis with Margaret as his mother. There is no documentation I have found to establish this and if fact Rowland's own account of his genealogy shows no Thomas. Subsequent genealogy of the Welch Tract in Pennsylvania also fails to show a Thomas Ellis as related to Rowland. Even the Quaker Meeting Minutes of the various Meeting Houses where both individuals lived fail to show any links between them. Many "believe" Thomas was his son because Thomas named one of his sons Rowland. Not very convincing since many Welsh settlers named sons Rowland.
So, if any one has links to Merionshire, Wales where records can be reviewed, if they exist, to indicate his parents or even siblings, it would be a great service to many of us still searching for his family in Wales.