Lea (Fallout 4)

trans-daughter of the sole survivor

Trigger warnings:  nothing comes to mind, besides potential dysphoria if you are a trans person so just to be clear: her birth name was Shaun, assigned male, she transitioned with hormones available at the Institute (and given the Institute's level of scientific advancements I'd say it's a permanent change even if no meds are available on the surface, she'll just have mood swings and little side-effects if she's not taking any), she didn't transition with surgery because she didn't feel the need, nor trusted their surgeons at this point but she's at peace with her identity. 

Canon divergences / my portrayal

Born Shaun, initially her story is the same as in the game, except that she's always felt 'different' and 'uncomfortable' until in her early teens she realized what exactly the problem was and started using the Institute's intel to research her situation, realizing that not only she was, in fact, a she, but that she could utilize the Institute's research and meds to help herself feel more comfortable in her own body. The change was accepted by the rest of the Institute in stride; she took the name Lea and that led her to start questioning herself, her identity and, unfortunately for the Institute, her beliefs and loyalties. In the triggers section above you can find a few more details about the transition.
This is what starts a domino effect, and while she still feels that synths are objects and nothing more, and still hates most of the factions out there and wishes for a better humanity, Lea decides to go see the surface for herself, a small trip that tells her living underground is also not the way to go. Basically she's unsatisfied with everything, but the last thing she wants is to lead the Institute, especially not after looking into her past more and feeling like she's their experiment.

And so, despite not believing in the Railroad, she secretly 'helps' them out of self-preservation, preparing herself to escape the Institute with one of the synths that will be rescued. She starts trying to change the Institute's minds about attacking the surface, but she knows she can't push too hard because the forces that ordered her kidnapping can still turn against her, and more importantly she creates a code that once activated will make the synths sent after her forget they ever saw her and leave, all of this in preparation for her escape. 

She plays her part, waiting for the chance to run away, blaming not only Kelloggs but the Institute for the death of Nora/Nate, and not knowing how to feel about the surviving parent that she never had the chance to know. At least at the beginning of her characterization she'd sell out anyone she considers a natural enemy for her own survival, and she's new to the surface but is bringing enough resources with her to pay for help.
She has a clone at the Institute ready to buy herself time before the synths are even sent to look. The clone if found by the Sole Survivor is meant to reveal that that is truly Shaun's appearance so that if her parent wants to find her on the surface they'll know what to look for. 

Your character can meet her in two ways:

-if they are a sole survivor, they can find her at the Institute just as she's ready to escape, whether she admits she's 'Shaun' or not depends on the thread, but she can also lie, use the fact that she helps the Railroad as proof that she's on the Sole Survivor's side because she's 'protecting innocents and that includes Shaun, who is now somewhere safe' until she can figure out what to do. She can use their help to escape (or, obviously, she can reveal/they can find out on their own that she's their daughter) and/or stay a little longer if the Sole Survivor is helping the Railroad so she can oversee a few more escapes to ensure that the Railroad will help her too. She may be awkward about their relationship, not knowing how they feel about her. I don't want to say more to avoid godmodding.
-if your character is not a sole survivor or if they are but you don't want them to meet at the Institute, Lea is living on the surface and has found meaning in "seeking knowledge" (not with the Brotherhood, they are still the enemy to her), traveling so she can discover new places and find pieces of history the Institute may not have shared with her. More importantly, she wants to understand how the surface works, what factions are out there, and so on, and what she wants without the whispers in her ears from all the people who tried to change her.  

Added: July 10th 2024