One stormy night, two couples burst in upon the same doctor, ready to deliver babies. Nora Allen was carrying twins, and Charlene Thawne one child—but the drunken doctor accidentally strangled the Thawnes' child. Attempting to make up for the mistake, he handed one of the Allen’s children to the Thawnes, convincing the Allens that one of their twins had been stillborn.
Malcolm learned of Barry's existence and the loving family that fate had decreed he would never know and used his gift for sorcery to give vent to his jealous rage.
He empowered himself with a mystic blue flame that was capable of stealing Barry Allen's superspeed. Barry's death during the Crisis on Infinite Earths appeared to have cheated Malcolm out of his dreams of revenge on his brother; instead, Malcolm focused on Allen's descendants traveling through time in a bid to exterminate them. The cold flame of his vicious alter ego, Cobalt Blue, ignited a family feud that endured for a millennium.
In the end, Wally West, the third Flash, ended the menace of Cobalt Blue by running so fast that Thawne's mystic gem overloaded from excess energy. Thawne was presumably destroyed; however, his gem, which contained Thawne's commanding consciousness, would be passed down to his hate-filled progeny.