The official telling of his birth is not pleasant. His mother, Non, was the daughter of a Ceredigion chieftain, over in the Pagan stronghold of West Wales. She was either seduced or raped by Sandde, then fled pregnant into the mountains.
David was born on a cliff-top, overlooking wild Cardigan Bay, in a thunder-storm. The pain of child-birth was so acute that Non scourged marks in a nearby rock; and the elements were in sympathy too. As soon as David's head crowned, lightning flew from the blackened skies and split the rock in two. Thus was Wales's patron saint delivered.
(Whoever thought that the Welsh were soft have never looked closely at any of our legends and folklore.)
However, look at that story again from a wider context and you'll see more than childbirth going on. David was the person who brought Christianity to Wales. Sandde is the Welsh translation of the Latin sanctus; in other words, holy, sacred, God. David was a child of God.
History can stick a prefix to the name of his mother all it likes, but St Non still bears the name of the Mother Goddess of the Britons. (See Ynys Mon (Anglesey); River Dee; River Don; the Irish Danu/Tuatha de Danaan; Devon (Dee's River) etc.)
Even in the mainstream telling, her name has been linked with all of the Arthurian personae, usually as the daughter of Cynyr (Connor in the Irish legends; Sir Ector in the English). Her tutor may or may not have been Merlin. Her step-mother may or may not have been Anna, an early name for Morgan Le Fey. In short, David was born from the womb of Paganism, as a child of God.
Christianity violently impregnated Paganism, leaving the old religion to flee into the wilderness. David's birth nearly killed his mother. Is that a hint of witchcraft I scent, in the way that the elements fought back, trying to destroy the newborn David?
Just in case there were any doubts left here, it's worth noting the position of Capel St Non (St Non's Chapel). It's on a headland, in a field, surrounded by neolithic standing stones, and contains a pre-Christian holy well bearing the Mother Goddess's name.