One drunken night, Jamie Madrox
spent the night with two women. At the same time. In two different locations. His mutant power to create duplicates of himself allowed him to be in two places at once. Unfortunately, neither version of Madrox knew what the other was doing. One slept with M
, the other slept with Siryn
. Soon after Siryn discovered that she was pregnant.
Although Siryn's life was far from normal, her pregnancy went relatively smoothly with few problems. Her friends and team-mates from X-Factor
were with her after she gave birth to a little boy whom she named Sean, after her late father Sean Cassidy
. When Madrox approached her bedside he was initially worried he would make a silly mistake, like dropping the baby. However, the happiness of the scene soon faded as the baby began to glow.
Baby Sean Madrox then slowly absorbed into his father's abdomen as if he was one of Madrox's own 'dupes'. Despite his mother's screams and his father's protests, Sean slowly disappeared.
It is believed that the Madrox who slept with Siryn was in fact the dupe; not the 'host' Madrox as had previously been assumed. Therefore, according to the theory, the son of a duplicate is itself also a duplicate; an infant duplicate. As such, when the baby physically came into contact with Madrox for the first time, it absorbed itself into the host body.
Due to Madrox's inability to release the baby from within himself, baby Sean Madrox has been declared dead. His short life had a terrible effect on both his parents, who split up soon afterwards.