While Lovecraft did not formally create a taxonomic system for his creations, the hosts of the Double Shadow (Phil, Ruth and Tim) – an excellent Podcast on the writings of Clark Ashton Smith – came across something very interesting in a letter Lovecraft wrote to Smith. The Double Shadow is the Clark Ashton Smith version of the excellent H.P. Lovecraft Literary Podcast, hosted by Chad and Chris.
If you are not familiar with Smith I strongly recommend you read his stuff. Before the Double Shadow Podcast I only read a handful of Smith stories (mostly his Lovecraftian stories) but with the Podcast as a guide it has been a blast reading Smith’s stories. I highly recommend the Double Shadow. In any event, Lovecraft included in a letter to Smith this taxonomy or genealogy on how both he and Smith are actually descendants of the Old Ones!
So based on Lovecraft himself, Clark Ashton Smith comes from the lineage of Tsathoggua (Smith’s own creation) and Yeb, which was child of Yog-Sothoth and Shub-Niggurath!
Also, according to Lovecraft, he is birthed from a “hellish and nameless tragedy between Viburnia and Ghoth the Burrower” (one of the Little People – Machen reference?). Strange to say the least! In any event, I thought this was amusing. Thank you Double Shadow! Next time I actually start talking about the biology of the entities, starting with the Shoggoths! Thank you.
Fred Lubnow
Lovecraftian Science 
Very funny! So H.P. Lovecraft’s descended from Nyarlathotep, Clark Ashton (or, as H.P. often referred to him, Klarkash-ton) Smith is descended from Yog-Sothoth, Shub-Niggurath, and Tsathoggua, and both are relatives of Azathoth! H.P.L. had a good sense of cosmic humor.
BRIAN
HPL and CAS certainly have fun with it! I have been reading a lot of CAS lately. Just purchased the Penguin Classics book “The Dark Eidolon and Other Fantasies” – very enjoyable!
Fred