In Culhwch and Olwen, King Kilydd's wife, Goleuddydd, dies in childbirth, leaving behind the king's only son. She tells him to go forth and remarry once two briar blossoms bloom on her grave, and he does so when the blossoms appear seven years later.
He finds a maiden to marry, kills her husband (another king), and plans to marry her. Then something curious happens (dramatic emphasis mine).
On a certain day, as the lady walked abroad, she came to the house of an old crone that dwelt in the town, and that had no tooth in her head. And the queen said to her, "Old woman, tell me that which I shall ask thee, for the love of Heaven. Where are the children of the man who has carried me away by violence?"
Said the crone, "He has not children."
Said the queen, "Woe is me, that I should have come to one who is childless!"
Then said the hag, "Thou needest not lament on account of that, for there is a prediction that he shall have an heir by thee, and by none other. Moreover, be not sorrowful, for he has one son."
The lady returned home with joy; and she asked her consort, "Wherefore hast thou concealed thy children from me?"
The king said, "I will do so no longer." And he sent messengers for his son, and he was brought to the Court.
I'm somewhat confused by the fact that the crone at first says that Kilydd has no children, then tells his new wife the truth. Even more puzzling, though, is that the king concealed his son.
My question is the same as the unnamed wife's: Why did Kilydd hide his son from her?