Lord Cassius was very curious when he found out Sophie existed from Keefe. Lord Cassius also was very suspicious of her and questioned her frequently. When the readers found out that Lord Cassius was not a member of the Neverseen, he later asked in Nightfall to join the Black Swan and is still involved in Sophie's life. He is, according to Keefe, "very good at blocking Telepaths". Like most Empaths, Keefe and Lord Cassius can sense Sophie's feelings from a distance. The blond hair would also make sense. However, this is a slightly unlikely theory because Lord Cassius is very prideful and, according to Keefe, "he'd never give up control of his kid like that —or be able to go this long without bragging about you."
Fintan is told to have blond hair, which would be one similarity between him and Sophie. He has always seemed interested in her, and he may try to destroy her, but that could be the only way he could get what he really wants. Fintan has shown no concerns in hurting people he's close to, so he would have no problem hurting Sophie too. This is a contradicting theory because Mr. Forkle said that he made sure she was not a Pyrokinetic.
Elwin always does whatever he can to fix her and all of her friends' injuries. He cares a lot about her. He has saved her many times. Elwin also goes out of his way to help her, by getting Mr. Snuggles for Fitz in Book Two, giving Keefe Mrs. Stinkbottom in Book 4, and giving Biana Lady Sassyfur/Betty-the-Yeti. He saves Sophie’s life so many times and prides himself in knowing that he will always make sure that the Moonlark is safe.
Quinlin was very surprised to find out Livvy was with the Black Swan, and that might be because he contributed DNA to the creation of Sophie. He also is shocked when Sophie turns up at his office for a probe. This is unlikely because he was involved in Prentice's memory break. He also searched for Sophie with Alden, which he would not have done if he knew more about Project Moon
Sir Tiergan is Sophie's Telepathy Mentor and is close to her, and he tries to help her in every way. Also, when he accepts to be Sophie's Telepathy Mentor, he appears to accept because of Prentice, (it is later hinted that he agreed so he could protect her), but he could also be accepting because he feels a connection with Sophie. In the first book, he also shows affection for Sophie. His personality also appears to be similar to Sophie's, they are both known to be rather secretive, and they both prefer to wear less noticeable clothing. He is also Granite of the Collective. Tiergan is a powerful Telepath, an ability he shares with Sophie.
- Human (Disproven)
One of her parents could have been human, giving her a stronger connection to humans. Also, instead of broadcasting her thoughts, she broadcasts her emotions. This is why Keefe and his dad can feel her emotions through the air. If one of her parents were human would mean that a human other than Amy knows elves exist, unless the Black Swan stole that human's DNA or erased their memories. This is a contradicting theory, because in Nightfall Mr. Forkle says that two elves donated their DNA for the project.
It may be possible because he is very protective of Sophie and loves her very much. He also has blond hair. This could be one of the reasons he decided to adopt her. Sophie also questions whether he is her grandfather when she is determining whether or not Jolie is her mother. However, this is slightly unlikely isn't much of a reason to keep this hidden. Although Sophie and Edaline would get angry if they discovered this, Grady would have probably told them by now if this was true.
Gethen could well be Sophie's father, as he is blond and has great telepathic strength. Though he fights against her, it may be all some sort of ploy, or he wishes that Sophie would become part of the Neverseen.
Alden shows a caring heart towards Sophie and his children. Alden and Sophie are both powerful telepaths. However, this seems unlikely because Alden spent 12 years searching for her, and he probably wouldn't have done that if he knew more about Project Moonlark. Also, he was involved in Prentice's memory break.
- Councillor Oralie (Proven correct)
Councillor Oralie has blond hair like Sophie. She knows the most about the Black Swan out of all 12 Councillors, and she helps Sophie out multiple times throughout the series, both legally and illegally. Mr. Forkle said that if people found out who Sophie's biological parents are, the world would collapse, and Councillors are not allowed to have a family. A Councillor breaking a major law could topple the world.
In Legacy, Sophie discovers that Oralie donated her DNA to Project Moonlark. Sophie is angry that Oralie never told her and their relationship suffers.
Brant has a very close collection to many people in Sophie's life. This is also connected to the fact that Mr. Forkle said that if people found out who Sophie's biological parents are, the world would collapse. Brant is in the Neverseen and panic could ensue if he was revealed as Sophie's father. This is a contradicting theory because Mr. Forkle said that he made sure she was not a Pyrokinetic. However, Jolie had many chances to extract his DNA.
Councillor Terik seems to support the Black Swan and Sophie. Sophie has access to his Imparter, and he has helped Sophie out in the earlier books. He was against the ability restrictor in Book 3: Everblaze. Terik is a Descryer, a unique Elvin ability like Sophie's teleporting. However, this is slightly unlikely because Mr. Forkle told Sophie that her parents did not know each other.
- Councillor EmeryCouncillor Emery is a suspect because in Everblaze, he tells Dex to put the restrictor on Sophie. While it harms Sophie, it could be Emery's way of trying to protect Sophie. However, this is unlikely because Mr. Forkle told Sophie that her parents did not know each other. Also, Emery doesn't seem to want to be part of Sophie's life.