"the birth of merlin" shares a significant relationship with "cupid's revenge," a play in the beaumont and fletcher canon. large-scale resemblances in plotting—the missing prince, the ruler and his heir who fall in love with the same woman—could be explained through derivation from common sources; but these larger-scale elements are supported by specific lines and passages that occur in both plays. compare, for example, "wilde-fire and brimstone eat thee!" in "merlin," iii,vi,108, with "wild-fire and brimstone take thee" in "cupid's revenge," v,ii, 49. other common passages occur in "merlin," ii,ii,35–39 and 72–81 and iii,vi,83–84, and "cupid's revenge", i,v,5–11, iv,i,2–7, and v,ii,44–48.