Who is Auk's mother?Whorl

As I re-read BotLS, I tried to pick out references to Auk's parentage. Around page 35 or so of Nightside, the sibs are talking about Auk and mention his parentage is a secret, much like Blood's. I originally thought Blood might be Auk's father, but there were no further clues along that line, and the secret of Auk's birth never comes again. While he's with Tartaros, he recalls his mother and remembers her name is "Lilly" -- Truth. but that's about all I could find regarding clues. My theory is he's a an embryo like Chenille and Silk. He seems to have their "staying power" when injured and he's picked out for the "engineering" theophany that lets him repair equipment. Also he's a born leader, able to get others to follow him to Blue. Any other thoughts? Rich Browne