Random Lists of TTS headcanons (mostly about Quirin and the Dark Kingdom) that I have:
Quirin became a Brotherhood member when he had a 'Home Alone' moment with Edmund and his wife because he thought they thieves (they broke in because it was raining HORRIBLY)
Quirin was in charge of the Brotherhood, in the sense that although Edmund as the King was in charge, Quirin was the one dealing with the group as a whole
There were more Brotherhood members, but they either retired, died or are simply lost in the world after the fall of the Dark Kingdom
The Brotherhood members had noble titles and pieces of land, Quirin had a BIG farming land (as the head in charge) and he used to help around before the Kingdom Fell. He used a few techniques he learned later on when he became a full time farmer (not all because different crops and different types of land)
You can find small communities from the Dark Kingdom moving around still, looking for some place to settle (and they eagerly go back to the Kingdom when Edmund starts rebuilding it)
The DK and Corona used to have a little bit of Beef because sun vs moon, that's why Quirin settling (probably with other people, lbh) there with the piece of the scroll was a good move
Corona was funded or helped fund by Demanitus
Demanitus is originally from the Dark Kingdom
Quirin was in the process of retiring when the Dark Kingdom fell
The Brotherhood all have specific face tattoos, but by the time Eugene was born they were only mandatory to use during events and things like that, hence why Quirin didn't have one, though if you wanted a permanent tattoo you could have it (hence Adira and Hector)
OR all the tattoos are temporary, Adira and Hector just have been reapplying theirs
The Great Tree used to be the border for the Dark Kingdom, hence why Hector set up shop in it
the Queen Ghost we saw was the one who helped fight against Zhan Tiri the first time around
Edmund (or at least, the Monarch that came before him) was the one who gave the Mind Trap to the Keeper, since he didn't have Any itent to use it
The place where the Mind Trap was was very Hush Hush, Cassandra only found out thanks to Zhan Tiri finding it out herself, BUT the existence of the Mind Trap was at least well known in the DK and was one of the 'cons' to joining the Brotherhood
The Mind Trap was originally meant to make sure that the Brotherhood wouldn't turn against the crown, the moonstone And to make sure that if a fight every happened, they would act in harmony. It's a 'made with good itentions, Very Bad Execution type of thing'
Eugene didn't reject his royal title from the DK, but he won't be it's King Outside of possibly becoming a temporary one until one of his and Rapunzel's kids are old enough to take over
To try and fix the plothole in season 3: people Forgot that Quirin was a Brotherhood member AND they had contacted (or at least TRIED TO) Adira and Hector at some point and they thought they weren't under Cassandra's control
Eugene grew a couple of inches between the movie and the series and that was because the two times he was healed by Rapunzel, he was healed
People either think that Cassandra was dead OR Cassandra was actually banned from Corona (and the Dark Kingdom) - she isn't getting away without consequences people
Varian had a therapist while in prison that he was forced to see, wether or not they worked or if they were a Saporian spy I haven't decided yet
The ACTUAL reason why the resistence against the Saporian was so small wasn't because of 'loyalty to the crown', it was because they had tried and it Blew on their faces and thus King Frederik and Queen Arianna aren't the only victims of memory wipe. Rapunzel doesn't know this because, well, would you admit to the rebellion to the crown?
Eugene and Lance, later on, are volunteers on Orphanages in Corona and Eugene got a LOT of funds given to them and goes to personally check to see if they are being used properly and that the kids are being taken care of well
the DK fondly call Eugene the 'fail prince' not because of anything he did but because his fighting skills are far below what the royal standard was.
I said this before but: The Queen of the Dark Kingdom trid to destroy the Moonstone, possibly because she was plagued by nightmares of what would happen in the future/of the stone hurting the Kingdom and her family