Im thinking Bo and one of his ex wives, maybe Didi or Sarah? They rewrite History all the time so why not let Rex be a Buchanan? His parents have to be someone that is active on the show right now.

Not that I'm pressed to give Rex more story, but if they were aiming to finally connect Rex to Bo, then they could easily spin it so that Sarah was pregnant with Bo's kid when Carlo kidnapped her, and she wound up giving birth (to Rex) during that year she was off screen in between Jensen Buchanan and Grace Phillips. Then Alex somehow got involved, being the woman who abandoned baby Rex at the hospital.

Chris wrote:

Not that I'm pressed to give Rex more story, but if they were aiming to finally connect Rex to Bo, then they could easily spin it so that Sarah was pregnant with Bo's kid when Carlo kidnapped her, and she wound up giving birth (to Rex) during that year she was off screen in between Jensen Buchanan and Grace Phillips. Then Alex somehow got involved, being the woman who abandoned baby Rex at the hospital.

Alex disguised herself as a homeless woman so that no one would recognize her and dumped the baby off. Good idea Chris, sometimes I think the fans should be writing for the show.