We've lost count of how many times these two have been separated, either by choice, curse, or terrible luck. Belle's been held hostage in a mental hospital, Rumple's died, ventured to Neverland, and been kidnapped by the Wicked Witch. And that was just in the first three seasons!
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.