When Pan's curse threatened to destroy all of their lives, Regina made the ultimate sacrifice. She undid her original curse, which wiped Storybrooke off the map. That meant saying goodbye to her son. Thankfully, the separation only lasted a year. Still enough time to break our hearts.
Henry's the glue that holds everyone together. And we're not just saying that because he has so many relatives. At the end of Season 2, Henry was kidnapped and taken to Neverland. His family banded together for the first time to rescue him from Peter Pan. Who turned out to be his great-grandfather.
Shortly after the original Dark Curse broke, Emma and Snow were transported to the Enchanted Forest. David stepped up to lead the town and take care of Henry as they searched for a way to reunite their family.