I think we have to look at Fate like a magnet. It draws all things into it. For me, it explains a lot. Rumple knew that Reggie was missing love because of Daniel and the lack of love from Cora. As a seer, he might have seen her interactions with Owen. He could have planted her wanting & needed a child within the curse. He could have also put something in the curse that brought the first born of the saviour to SB and in turn brought the Saviour. He is afterall Rumplestiltskin and does procure first born children. It all comes down to the curse and fate like a magnet, drawing in everyone involved.
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Keeper of Pandora's Box & The Yellow Brick Road.