I wanted to ask a question of Prydain fans: who is Gwydion's father (and his mother, for that matter--amazing how many missing moms there are in the chronicles)? People tend to be identified by whose son they are (if male) or whose daughter they are (if female), with orphaned Taran being an obvious exception. Yet isn't Gwydion always simply referred to as the Prince of Don? We know he is descended from the Lady Don, and he becomes High King after King Math's death, which implies he is in some sort of close relation to the king. But we don't ever hear Math described as his father, do we, nor do we hear of Gwydion as a nephew or something. Correct me if I'm wrong. I couldn't find anything about Gwydion's parentage in Michael Tunnell's A Prydain Companion.
I also had some information on a treat for Prydain fans. In case you haven't read this yet, there is a great interview with Lloyd Alexander in a book about fantasy writers. Here's the citation: The Wand in the Word: Conversations with Writers of Fantasy, ed. Leonard S. Marcus. Enjoy!