There are two main issues with Cora being Bae’s mom and him being twins with Regina. Firstly, Rumpelstiltskin is centuries old (as confirmed by Jane Espenson, the writer of episode 1×12). That means Rumpel lost Baelfire centuries before Regina enacted Dark Curse. Regina isn’t more than about 32 when we see her in FTL. On the FTL timeline, it just doesn’t pan out. Secondly, Rumpel was not yet cursed as the Dark One when Baelfire was born and was just a regular man. In the tale of Rumpel and the miller’s daughter, Rumpel was already cursed as the Dark One when he asked for Cora’s first-born as part of a deal for turning straw into gold.
………Good Points 😳 Thats what happens when your imagination runs off without allowing your logic to tag along for the ride I suppose 😆