Admin Note: At this time, the information on this page is mainly theories and headcanons, as none of this has been confirmed by Shannon Messenger.
The Theory Edit
Many people think that characters in Keeper of the Lost Cities are LGBTQ+, a likely occurrence due to the high population of LGBTQ+ citizens of the world.
Many people think Dex is bisexual. This is shown through many instances and ships such as Detz/FedEx. Some people think that even though Dex doesn't hate Fitz anymore, he can't possibly like "Wonderboy" even if he stopped with the nickname, but others believe that the nickname is just a way of Dex trying to hide his feelings. He is also headcanoned as genderfluid, pansexual, nonbinary, and/or demiromantic. He is often shipped with Keefe (Keefex/Dexeefe).
Many people headcanon Biana as bisexual (Bi-ana), but others headcanon her as lesbian, dubbing her "Lesbiana" and pairing her with Sophie (Sophiana/Biophie), Marella (Marelliana/Biella), Linh (Linhiana/Binh), Stina (Stiana/Bina) or both Linh and Sophie (Solinhiana).
Some people think Sophie is bisexual, asexual, pansexual, nonbinary, demigirl, gray-ace, or lesbian, though it is not clear. She is shipped with Linh (Solinh/Lophie), Biana (Sophiana/Biophie), both Linh and Biana (Solinhiana), and/or Marella (Sophella/Marphie).
Keefe is widely headcanoned to be bisexual, pansexual, asexual, or gay. Some people ship him with Fitz (Feefe/Keefitz), Dex (Deefe/Keefex), Tam (Teefe/Kam), or both Biana and Tam. He flirts with most people, so we do not have much ground on who he likes other than maybe Sophie. He has also been headcanoned as trans, genderfluid, and nonbinary.
Tam is headcanoned by many as gay, bisexual, nonbinary, demiromantic, demisexual, aromantic and/or asexual, and shipped with Keefe (Teefe/Kam) due to them hating each other, similar to Drarry (Draco Malfoy and Harry Potter from the Harry Potter franchise), and with Fitz (Titz/Fam), Tam likes Fitz in some way, he likes his hair and suit. He has also been headcanoned as transgender due to it being impossible for identical twins to be born of opposite sexes.
Linh is mainly headcanoned as asexual and/or lesbian and liking Sophie (Solinh/Lophie), Biana (Linhiana/Binh), both Sophie and Biana (Solinhiana), or Marella (Marellinh/Linhella). She has also been headcanoned as trans, similar to Tam.
Fitz is widely headcanoned as bisexual, transgender, gay, pansexual, genderfluid, and many others. People ship him with Dex (Detz/FedEx), again due to their supposed rivalry in the beginning of their friendship. People also ship him with Tam (Titz/Fam), or Keefe (Feefe/Keefitz) due to them being best friends.
Marella is headcanoned as being lesbian, pansexual, or bisexual and being romantically involved with Sophie (Sophella/Marphie), Biana (Marelliana/Biella), Stina (Stinella) or Linh (Marellinh/Linhella). She is also headcanoned as aromantic and/or demisexual.
 Alternating between sexualities, or not having fixed sexuality. Sometimes said to be "permanently questioning" or "sexualityfluid".
Attracted to males and masculinity from all genders.
 Identifying as having no gender.
 Not romantically attracted to others. Can still be platonically, aesthetically, sexually, or sensually attracted.
 Not sexually attracted to others. Can still be platonically, aesthetically, romantically, or sensually attracted.
Mainly attracted to one gender, but occasionally attracted to another gender. (See homoflexible and heteroflexible)
 Identifying as any combination of two genders.
 Attraction to two or more genders.
 Someone who identifies with the sex that they were born with.
Identifying partially as one gender (male, female, nonbinary, etc.), but partially as another (nonbinary, female, male, agender, etc.). This may be aligned with one's biological sex, or not.
Only attracted to those that they've formed a strong emotional connection with.
Only attracted to those they haven't formed a strong emotional connection with.
 Attraction to the same gender. (Lesbian refers to female homosexuals only, though Gay can refer to male and female as well as Homosexual)
Alternating between genders that are never masculine.
Alternating between genders that are never feminine.
Alternating between genders, or not having a fixed gender identity.
Alternating between genders that grow in intensity over time.
Someone who does not identify as male or female all the time.
Only experiencing sexual attraction at certain times or in certain situations or to certain people.
Only experiencing romantic attraction at certain times or in certain situations or to certain people.
Attracted to females and femininity from all genders.
 Mainly attracted to the opposite gender, but occasionally attracted to other genders.
Mainly attracted to the same gender, but occasionally attracted to other genders.
 Stands for: Lesbian, Gay, Bisexual, Transgender, Queer/Questioning, and more.
Experiences sexual attraction, but does not want to be in a relationship.
Attraction to all genders, but does care about gender, so has a preference towards some genders.
A gender/gender spectrum outside of the male/female binary spectrum. Can also be used as an alternate term for genderqueer.
 Identifying as any combination of all/multiple genders.
 Attraction to all genders, or attraction to people regardless of gender.
 Attraction to multiple genders or all genders.
 Transgender means you were born in a body opposite to the gender you actually are. For example, you were born with the body of a girl, but you are a boy.
 Identifying as any combination of three genders.
 Someone who is unsure about their sexual/romantic orientation and/or gender identity.