I definitely, definitely remember reading at least one interview with Tom talking about Loki and Thor’s dynamic, and according to him, Loki is the younger brother. Now, this was a few years back, before Ragnarok, so hey- maybe somewhere along the way Loki became the younger of “twins”, but certainly, the way Tom (and therefore presumably Chris too) sees it and approaches it and plays it, Loki is definitely the younger brother to Thor’s big brother.

The wonderful thing about fiction is that it’s subject to many interpretations, and the wonderful thing about fanfiction is that it allows a large number of people to explore a large number of those possible interpretations. I’m certainly not a “death of the author” type who thinks a work of literature can mean literally anything a reader sees in it – the text does provide some constraints – but it always leaves a lot of things under-determined. I think this is one of those issues where the text points in different directions at different times, so readers are free to follow either path.