Charmed

 What happened to Phoebe and Cole's baby on Charmed?

That baby was an unlucky victim of the manipulations of the Source and the Seer: he was conceived in a dark Wedding and with the Seer putting a Fertility Potion in Phoebe’s chocolates to speed up the process, then (still in the womb) he was influenced by the Source (who had Possessed Cole) into trusting and loving him, and at the same time the Seer drugged Phoebe with a tonic that would suffocate the good side of the little boy (and he did manifest powers that were typically demonic, like the ability to generate fire and electricity, Possession and Teleporting through flames). After the Source/Cole was vanquished by the Charmed Ones, he used his own powers against Paige (because he blamed her for the death of his father) and to hurt people whenever he felt “threatened” or felt like Cole was badmouthed, thus stressing Phoebe and making her physically sick. After the Seer transferred him into her own womb, she revealed that the baby was “hers” because she had planned his conception and molded him into a force of evil and the new Source (through the black wedding, the tonic and the influence of the Source/Cole) thus preventing the child to become the rightful heir to the Charmed Ones’s power. The Seer then tried to destroy the Charmed Ones, who forced the little boy to use his full powers against them, but those powers were too strong for an unborn baby to bear, so he was destroyed alongide the Seer.