Elizabeth Sydenham had no children by either Sir Francis Drake or Sir William Courtenay, so you are certainly not a descendant; even if you were, an autosomal DNA test would be unable to confirm a relationship that far back -- the limit of usefulness of autosomal testing is around 10-12 generations, since DNA is lost in every generation due to recombination;the chance of having an autosomal DNA match with a tenth cousin (who shares ninth great-grandparents) is one in five thousand.