Merlin and the Lady of the Lake did have offspring, though Merlin could not physically have children. He chose to live a hermit's life because he lived with the Lady of the Lake. The Lady of the Lake and Merlin had a spiritual child, who later reincarnated as Arthur.

The name of Merlin's horse was Ruber.(1) The sea line was rough and the banks were rough, the land was rough. The dagger(2) of the kings was lifted with the light.

(1) " ru'b/er -ri a. red. mare -rum Red Sea; Persian Gulf. oceanus - Indian Ocean. Saxa -ra stone quarries between Rome and Veii." Collins Latin-English, English-Latin Dictionary, p292.

(2) Excalibur