One interesting fan theory posits that Avatar: The Last Airbender’s Sokka of the Southern Water Tribe is the father of Senna, Korra’s mother in The Legend of Korra. Since 2012, audiences have speculated about what happened to Sokka, beloved jester, non-bender strategist, brother of Katara, and companion of Avatar Aang in Avatar: The Last Airbender. Sokka is the only member of the original Gaang (besides Aang) who is deceased before the beginning of the ATLA spin-off series, to much disappointment and postulation. What happened to Sokka between the events of Avatar: The Last Airbender and The Legend of Korra has been a matter of much debate.
The hit Nickelodeon shows follow two cycles of the Avatar. The Avatar is the protector and peacekeeper of the world and the only bender able to master all four elements: water, earth, fire, and air. Avatar Aang is woken from his 100-year slumber by Sokka and Katara of the Southern Water Tribe, who then join him on his quest to master all four elements and defeat the tyrants of the Fire Nation. Avatar sequel Legend of Korra takes place 70 years after the events of The Last Airbender and offers very little information about Sokka’s adult life, even as the other members of the Gaang have moderately enlightening cameos throughout the series.
There are endless fan theories about Sokka, simply because the popular character’s later years largely remain a mystery. Many theories center around who Sokka ended up marrying and whether or not he had any children. A little-known but intriguing theory connects Avatar Korra to Sokka through Korra’s mother, Senna. The theory speculates that Sokka could be Senna’s father, the grandfather of Avatar Korra. Since Sokka’s adult life is generally unknown, it is possible that he and Suki moved to the Southern Water Tribe after the events of Avatar: The Last Airbender and raised a family there.
The relative lack of information about Korra’s mother, Senna, allows the theory to grow further since Avatar Korra was born and raised in the Southern Water Tribe. Though he was also the Southern Water Tribe representative on the United Republic Council, Sokka likely spent much of his time in the Southern Water Tribe, especially since he eventually became the Chieftain of the Southern Water Tribe like his father before him. Korra's father, Tonraq, is from the Northern Water Tribe, but Senna's past is not elaborated upon. The fact that Senna's parentage is not touched upon leaves space for audiences to build the theory in favor of her being related to Sokka.
Admittedly, it probably would have been mentioned in the show if Sokka and Katara were actually related to Avatar Korra, especially because Avatar Korra was so close to the family of Avatar Aang (and maybe a discussion about Korra being her own great uncle is best left to the imagination anyway). It is, however, interesting to consider how this theory heightens the already unique bond between Korra and Katara, connecting the generations between Avatars in a completely different way.
Ultimately, this theory imagines a relatively happy life story for a beloved character whose absence in the spin-off show was a great disappointment for many. That Sokka may have married Suki and lived out his life in the Southern Water Tribe surrounded by family and friends is a conclusion that many fans would most likely welcome, especially since canon material offers little to no information on the subject. The satisfying theory gives people something to think about while tying Avatar Korra to Aang's Gaang even further, making the bond between the characters of Avatar: The Last Airbender and The Legend of Korra both spiritual and familial.