What if Regina had a son the same time, Snow and Charming had Emma? The son of darkness and the daughter of light. Imagine if the two ever met. Could it bring peace or spread chaos? Except when doing the curse, Regina did not realise that her son would be taken away but not the same way Emma was. They both eventually come back to Storybrooke. Like Rumple said "All Magic Comes With A Price". He also said that the curse would leave a feeling of emptiness in Regina.