Siderfin Family

I have had the opportunity to spend some time studying the Siderfin family of Somerset (principally Luccombe, Luxworthy, Selworthy, Dunster, Minehead and Wootton Courtney). My 3x great grandmother was Elizabeth Siderfin daughter of Robert Siderfin. I have had a couple of queries about the genealogical chart which was produced in a book on the Siderfin family. I myself was somewhat perplexed by the Chart but the individual who wrote the book would have likely had knowledge of his mother's first and second cousins so felt that his chart may have been somewhat more accurate than my own studies on this family. However, as I read and reread his book I am realizing he may have been mistaken in his tracing of my direct family line and that they were actually descended from Augustine Siderfin rather than his uncle Robert Siderfin. Augustine was the local school teacher and my 2x great grandmother was also a school teacher as well as her older sister. My 3x great grandmother signed her marriage registration in 1792. I had linked one of her sisters to the Nurcombe family but in his book he notes a Nutcombe family. I need to work my way through an extensive will that mentions all the siblings of my 3x great grandmother and discover the relationship of this individual to the family and it may well be the clue that lets me link back through Augustine. Robert (current father of my Elizabeth) would have been 103 when he died and over 60 when he married  so I have always debated it somewhat because of the enormous age disparity. Robert, son of Augustine has always been a possibility.