Steve, you're absolutely correct. The Welsh Genealogies, AD 300-1400 by Peter C. Bartrum don't show a child named Jonet to Bleddyn ap Cynfyn.
If anyone knows how to fill in the gap, please let me know. Dvytca@gmail.com
David it sounds like the parent child relationship needs to be removed. PROs can do that from the child profile (full view) > relationships tab > (tick off parents) remove button (save & continue). Then go the "about" tab & enter your excellent source citation & that you've disconnected from the impossible parents, a link to their profile is helpful.
Once the bad connection is broken (tree is split) it will be much easier to build accurate lines on both sides.