Well, after posting
this news everywhere last night, someone pointed out the anomaly that Joanna Fitswilliam was born nearly 150 years after her "mother", Eleanor of Lancaster, died. I figured there still must be some connection, but that piece of logic ended up actually bursting my bubble.
I did a lot of research tonight and none of it connects Eleanor of Lancaster to the wife of Edward Fitswilliam (Joanna's father). There is no record of who was Edward Fitswilliam's wife was, but it certainly wasn't someone who was dead for nearly 150 years. Someone apparently filled in the dots on his own tree and it was published into the OneWorldTree.
You can see the
results of the search of the OneWorldTree here. You can see many others have Joanna Fitswilliam in their own trees, with different parents. The one I happened to choose last night was the third one in the list.
I have the truth now, and although it's not NEARLY as exciting, it's still extensive (pretty good that it went into the 1300s) and that's all I really wanted.