There are number of poems that are attributed to Myrddin found in the Black Book of Carmarthen. From these poems I was able to derive the relationship between him and his sister Gwenddydd. Myrddin may have been responsible for the killing of his nephew, son of Gwenddydd, in the Battle of Arfderydd.

It is from The Diaglogue Between Myrddin and his Sister Gwenddydd preserved in the Red Book of Hergest, where I found the name of Myrddin's father and possibly his four brothers. Myrddin and Gwenddydd were said to be twins.

See the Welsh Legend of Myrddin.

The source for the family tree of Caldonius Merlin, come from Geoffrey of Monmouth's Vita Merlini, written in 1150 (see The Wild Man of the Woods). Geoffrey had also written Historia regum Britanniae in 1137, where Merlin first appeared as a boy and advised the King Vortigern about his crumbling fortress walls. People have speculated that Geoffrey was writing about two different Merlins.

Geoffrey of Monmouth may have got his own sources from the Welsh poems attributed to Myrddin, and from the Scottish legend about Lailoken.

The family tree is based upon the account in Historia Brittonum, which Nennius had written in the 9th century. Geoffrey of Monmouth had based his Historia regum Britanniae (c. 1137) upon Nennius' work, changing and elaborating the event where Vortigern tried to build a fortress, but its walls kept tumbling down.

In Nennius' account, the "boy born without a father" was named Ambrosius, not Merlin. Ambrosius is actually a Roman name for Emrys. After Ambrosius (Merlin) told the king what was causing the wall to collapse, he claimed that his father was a Roman consul, compared with Geoffrey claiming the boy's father was the devil or an incubus.

See either the Boy Prophet or Vortigern about this event.

The genealogy above, is based upon the Historia regum Britanniae, written by Geoffrey of Monmouth, in 1137. Geoffrey was the first to use the name Merlin (or Merlinus, since he had written the Historia in Latin).

He elaborated the scene, found in Nennius' Historia Brittonum (c. 9th century), about Vortigern trying to build a fortress, which kept collapsing. It is this scene that Vortigern met Merlin. Through his mother, Merlin was the grandson of the King of Demetia (Dyved). Merlin was the son of the devil (or incubus), but because of his baptism at birth, he had great wisdom and the remarkable ability to foretell the future. After Merlin finished explaining why Vortigern's fort kept collapsing, he revealed that his name was also Ambrosius.

See either the Boy Prophet or Vortigern about this event.

Geoffrey doesn't give us that much detail about Merlin's extraordinary birth. This was written by Robert de Boron, in his trilogy of verse romances about the Grail.

Robert de Boron was a French poet, who wrote a trilogy about the Holy Grail (c. 1200): Joseph of Arimathie, Merlin and Perceval.

It is in Merlin that Boron wrote an account about Merlin's birth. This poem also give account about the birth and fosterage of Arthur, Arthur becoming king when he drew a sword out of anvil or stone, but the account is fragmented. There is a prose version on Merlin, found in one of five works of the Vulgate Cycle.

Here, Merlin was indeed the son of the devil, but because his mother was a devout Christian, baptising her son immediately after birth, Merlin was not an evil creature of Satan. He retained his demonic power to know everything that had happened in the past, but he was also given God's gift to see the future.

We discovered that at birth, Merlin was named after his grandfather.

You will find an account about Merlin's birth in Timeless Myths, titled Son of the Devil?