Both women were born into royalty while the men were born as commoners but married into royalty.

Both couples met in the Enchanted Forest and then had a second "first meeting" in Storybrooke after losing their memories due to a Dark Curse.

Mary Margaret and David believed they were having an affair while he was truly married to her and not Katherine. Regina and Robin believed they were having an affair before it was revealed that his first wife Marian hadn't been saved.

Snow and Charming were separated when he initially chose to maintain his engagement to Abigail, and again while cursed when he...