Sylkior

Sylkior is the family/poly ship between Loki, Sylvie Laufeydottir, and Thor Odinson from the Marvel Cinematic Universe fandom.

Canon
Loki and Thor are brothers, and Loki and Sylvie are variants of each other from alternative timelines. Due to the time-travel aspect of the Loki series, there are some variations in the canon/history of each character in this relationship.

The version of Loki in this ship is the Variant from the 2012 New York Time Heist, who grabbed the tesseract and transported himself away and was apprehended by the TVA. Loki last saw Thor in New York in 2012, after his defeat (in the Avengers film). After Loki is apprehended by the TVA, he is shown a video of how his life was meant to proceed. He witnesses working together with Thor again and their reconciliation, and he smiles when Thor says to Loki that he might even give him a hug (in the film Thor: Ragnarok). Loki also witnesses his would-be future self attempt to kill Thanos and his own death, and that Thor embraces him as The Statesman explodes. Although Loki is told that he cannot return to his timeline (and to Thor), he remains interested in trying to speak with the Time-Keepers to do so. For this reason, Loki begins working with the TVA to track a Loki variant: Sylvie.

The version of Thor in this ship is typically the one following Avengers: Endgame. This version has additional history with his brother Loki who died (in Avengers: Infinity War), which the 2012-Variant version of Loki has not directly experienced -- although Loki is aware of it from the TVA footage. After Thor witnesses his brother's death, he is deeply affected by it, and it drives him to revenge against Thanos. Over the following years, his depression/trauma of losing Loki manifest is multiple ways: not being emotionally well, gaining weight, and not being an attentive king of New Asgard. During a time heist to retrieve the infinity stones, Thor sneaks past Loki's cell in the dungeons, and does not try to interact with his brother to avoid changing the timeline. Thor is not aware that a version of his brother is alive, and he has never met Sylvie.

Sylvie is a Loki variant from a branched timeline where Loki is a girl. When she was a child on Asgard, the TVA apprehended her for an unknown Nexus Event (which would cause a timeline branch), but she escaped and lived time-travelling on the run, and she took the name Sylvie. She and Loki meet while Loki is helping the TVA track her down, and Loki ends up going with her. They get closer, begin working together, and develop romantic feelings for each other. Together they confront He Who Remains, the man behind the Time-Keepers and the TVA, with the intention of killing him and freeing the timeline. But when He Who Remains tells them of the risk, Loki hesitates to consider, but Sylvie wants to go forward and kill He Who Remains, so Loki and Sylvie fight. Sylvie kisses Loki, but she pushes him through a Timedoor and she kills He Who Remains, leaving her and Loki separated across time.

Quotes
"God. Now I understand why Thor found this so annoying."

- Loki during his first conversation with Sylvie in Loki episode 2 "The Variant"

Fanon
Since Loki and Sylvie are variants of each other, many fans believe that Thor would embrace Sylvie as a family member. The three are also shipped romantically.

Fans began taking an interest in the ship following episode 3 of the Loki series, and the term Sylkior came into usage on social media. After Loki and Sylvie bonded on Lamentis in episode 3, fans began to ship Loki and Sylvie both romantically and platonically as being like long-lost twins, and fans began to imagine their relationship with Loki's brother Thor as well.

The ship is still very new, and there are very few fanfics for them, with only six on AO3 one week after the Loki series ended.

Fandom
FAN FICTION

TWITTER
 * Family portrait by @mjarmerchant
 * I love them & want them to be a big awkward family by @solidafg
 * Sibling bonding time by @MysiePereira
 * Siblings? Siblings by @octisquad
 * Sylvie meets Thor by @octisquad
 * Sleeping by @sensoriumz
 * Sylkior in bed (semi-NSFW but not explicit) by @ponderosa121
 * Meme "This is my boyfriend Loki, & this is Loki's boyfriend Thor" by @PrettiestThor
 * OT3 meme by @feelmynoize
 * Love them by @MorgenSevermalt
 * Ragnarok Thor won the Sylkior poll! by @moopzies
 * Sylkior makeouts by @moopzies
 * He is bisexual (他是双性恋呀) by @_Micias_

TUMBLR
 * Another! by lousysharkbutt
 * "Wow Loki you were right! Your Thor is indeed hot" by deraniel

Variations

 * Thorki refer to the ship between Thor and Loki
 * Sylki refers to the ship between Sylvie and Loki