I didn’t see any credits for a brother or other young boy. So, I’m thinking that sort of squashes the Rumple/Pan/Bro theory. It’s looking more and more like Malcolm is his father. I also think that Pandora’s box doesn’t actually hold anything, rather it contains the magic that allows you to hold evil somewhere. In this case, young Rumple wished for his father, the father of all evil fathers, to be contained in NL.