If we assume that Cayt is approximately 15 years old, as she looks, and that I am her father, then her mother is likely to be one of two women.
When I was living at Tuldis Castle as a guest of King Ramiro I was involved briefly, but quite intensely with Lord Justin's daughter, Camille. Six years my elder, Camille's experience with love and lovemaking far exceeded my knowledge at the time. She was totally enchanting. I dare say that she is one of the few women who have truly seduced me. Camille had a dominating will and was fiery and moody at times which would account for Cayt's temperament (what little I've witnessed of it) Camille might well also have not told me about the child. There's even a chance that she wouldn't have even raised the child herself.
Little over a year later while I was studying at Cambridge I fell in love with Bronwyn Joueur D'escheque. Bronwyn was quiet and withdrawn, but she was an outstanding scholar who had the ability , it seemed, to recall the slightest detail of any knowledge she had ever been exposed to. Only I was able to coax this woman out of the library to enjoy some of life's non-academic activities such as swimming, horseback riding, and dancing. Even though we followed our own independent pursuits, Bronwyn was with me many a night as I wrote my Treatise on Magic. After Blaise's disappearance and the completion of my academic work I longed to spend more and more time with her. In September I proposed marriage to her. She declined in such a way that I was convinced of her reasons and motives, but upon reflection I cannot say what these reasons truly were or why I was so easily persuaded by them.
The piece that does not fit well is that Bronwyn would have told me about the child. She was very honest and forthcoming. She knew well that I would want to know I had a daughter, and that I would return to them when I received word. Still, Bronwyn was a woman of immense wisdom. Perhaps it was exactly the knowledge that I would return that kept her from telling me. She might not have wanted to burden me with the responsibility of raising a child, though it seems outside her nature to deny me the opportunity.
I'll note that I had not yet developed the spell of Adjustable Furtility at the time that I knew either of these women, so the chances of concieving a child would have been left to nature.
There is also the possibility that Cayt is not as old as she looks. After all, had I not matured faster than those around me? In the five years between the time I left Cambridge and the time I met up with Aurthur I had a number of not very deep or meaningful relations with a number of women. Among these, the only one that stands out strongly was a two week span that I spent at Windsor Manor with Lady Vylette of the Stone, a knight and daring strategist. Vylette was stunningly beautiful, disarmingly charming, and one of the wildest and trickiest knights I have ever met. (One could even go so far as to say Vylette was downright underhanded) She had heard rumors about me and was fascinated to meet the mysterious Myrlyn. The poor Duke of Windsor had his hands full during those two weeks suppressing rumors (many of them true) of the scandalous goings-on between us. Though the flame burned brightly between us it also burned briefly. Soon Vylette turned her attentions to other things, as did I. Word got back to me that Vylette had been killed in battle not three months later. I was never able to confirm this, however. Furthermore I had employed my spells in an attempt to ensure there would be no child conceived while with this warrior, who clearly had no interest in bearing a child, but the two of us spent a few nights in altered states. It's possible, however slim a chance, that in one of the nights that things got out of hand and the proper spells had not been cast, and just maybe tales of Vylette's death have been greatly exaggerated. It would not be above her to fake her own demise.
Then there are Arthur's sisters Marlys and Gwend'llyn. I had affairs with both of them on and off over the years. Marlys, the older of the two, is very outgoing and forward. She propositioned me the first night we were together. Arthur is somewhat uneasy in her presence. She orders him around and makes playful light of his follies, which unnerves the man to no end. I, on the other hand, feel very comfortable around Marlys. She's friendly and very easy to talk with.
Gwend'llyn is very competitive and likes to one-up her sister. The two of them have very similar looks about them, with the same long golden hair, brown eyes, and medium build. Once she visited me in the guise of being Marlys. It's not so easy to fool a mage with such a simple ruse, but I played along, and I'm glad I did. (although she was steamed when she found out I had known all along.) Gwend'llyn is one of the most loyal friends I've ever had.
One glaring problem with the theory that one of Authur's sisters is Cayt's mother is that Cayt would be maybe 7 years at the oldest, which seems very unlikely. Additionally, I can't imagine either of them being able to keep such a secret from myself or even Aurthur.
There are other possible explanations for her age. Clearly Cayt has found her way through shadow. I can not imagine how she has managed that a mere week after I found my own way to Amber. Never-the-less, she could have traveled through shadow long ago, or even been raised in a different shadow than she was born in. Jessica has described to me a hellride she managed at age 5. Something like this could have happened with Cayt. With the time fluctuation from one shadow to another Cayt could have been born at nearly any time in my past.
For all I know there is some way that she could exist before she's even been born. Don't ask me to explain this. I have seen so much I had believed impossible in this last week that little would surprise me.
Let's not overlook the possibility that she is not truly my daughter. I will have to make a subtle effort to confirm this point. She could be the daughter of another Amberite, or she could be a spy, or merely misinformed.
One thing I do know is that I will have to be extremely careful over the next few days to make sure Cayt does not meet the same fate as poor Nathaniel.