How much more complicated would it make things if Arathorn was a trans man? He and Gilraen can't have a kid because of that, but they WANT one (also there's the whole thing about the line of kings and needing a blood heir, but that's secondary here) so, they need to do something about that right?
So, a plan is hatched. A list is drawn up!
A) They need a male with the relevant bits. B) It needs to be someone very certainly NOT anyone they know to be politically awkward. C) It very very much needs to be an individual disinclined to claim the child and cause trouble. D) It needs to be someone Arathorn and Gilraen are comfortable bedding a few times (A: ... well, you wouldn't have to if you don't want to? G: Shuddup, we are doing this TOGETHER.)
That .. kind of rules out a lot of people they know. Most of the rangers, most of the people that live in Imladris.
BUT THEY FIND A PERSON. (And if maybe one of those points up on that list is brushed aside, well ¯\_(ツ)_/¯)
Maybe it's a simple married couple and genetic material donor have several encounters and then the donor walks away after a child is made thing. Maybe it became more than that. No one is telling.
However it goes, Aragorn happens!
Everything is fine and there's no fallout and- then Arathorn dies. And Gilraen takes their son to Imladris.
And Elrond takes one look at a child that definitely has FAR more than a trace of elven blood. And very familiar eyes.
E: Wh- who did you say you chose, when you and Arathorn decided to have a child?
And that's all she'll say. Elrond managed to get her to confirm the friend was an elf, but that's all she EVER says.
... But Elrond knows those eyes. The curve of that jaw. Those curls are perhaps coarser yes, as edain hair often is. There is undeniably a great deal of Arathorn in the child, yes, but many traits that clearly came from elsewhere.
He wrapped his own small hands in hair like that a very very long time ago.
He can't not see Maglor Feanorion in his own foster son any more than he could unsee the sun. It's never confirmed, but-
Elrond has a headache (and a heartache).
Aragorn is a peredhel AU!
Aragorn as Maglor's kid AU!
How much would this screw up things? Depends! Is Aragorn mortal, or does he have a CHOICE to make? *shakes the box of dolls gleefully*
I kind of like the idea of a have your cake and eat it too thing where Aragorn and Arwen still become King and Queen of Gondor, but its kind of like they're more of regents laying the groundwork for whichever child of theirs chooses mortality. Arwen Knows at least one will, she's Seen it.
It's nonsense I know, but it's FUN nonsense.