Sorry but your query is a little confusing.
So you have a Susannah Thorn, Parents unknown Thorn and Mary nee Purefoy?
Marys Parents Edward Purefoy and Anne?
Susannah married Rod Dudley and had a Son Thomas?
ROGER Dudley married Susan THORNE 8 June 1575, Lidlington, Bedfordshire
(Familysearch.Org)
So your 1588 Marriage date is out.
Trish
