I too am a descendant of John Seymer/Seymour, and have tried very hard to discover clues to his parentage which has been generally considered unknown and perhaps unknowable. My data can be found in the his profile inmy Martin Family Tree at Ancestry.com (https://www.ancestry.com/family-tree/person/tree/38637635/person/28...).
i would be very interested reviewing the evidence you and your aunt have found, and I will be glad to share my thought about the possibility of what I call our ignoble connection to British nobility.