I really really hope that this is NOT the case, let Mari have her own background & mythology rather than being tied to a popular canon character.
"The fan faves secret sister" is bad OCs 101.
Like it can be done but with no buildup? They look nothing alike, & aren't they wildly different nationalities anyways? So how would that work, one Japanese woman boinked one British dude and a german one, but then wouldn't the Japanese surname at least be the same....
I've always assumed the "strict catholic highschool & lots of pets" backstory 'cause it explains Mari well enough (she's all eccentric cause she had to suppress her inner weirdo, & that's also why she dislikes authority & likes to work on her own etc., though being in a boarding school might also have led her to be relatively independent & cool-headed) & I hope something likes it gets made canon, though it's fully possible at this point that we won't get much backstory because there is just so much to wrap up & mari's ultimately a supporting character.
I mean they considered that whole "Mari steals Asuka's job" premise in the CR & then rightly decided to scrap it, though the rivalry still made it into Q in a way that doesn't rob Asuka of all her cool moments. "relatives" or "lovers" arent the only possible relationships out there why is comrades or rivals not good enough?
As for Kaworu: Personally I'm really critical of the whole "EVA is all traps and ifucks your and ndex finger wagging fingers and cautionary tales" interpretation, from the show itself and the interviews the impression I get is that it's a very personal meditation of the human condition, a record of how someone perceives the experience of & truth about life, a depiction of feelings, & yes, realizations, too, but not from the PoV of the teacher wagging the index finger but someone reflecting their own shortcomings from experience. It's not so much "if you do this you will fail" as it is the experience of parting & failure
Like this is something that got started when EoE first came out & ppl were very much wanting a more "physical"; and then the perception of it was that it was bleak & unsatisfying & incomprehensible,& so the idea crystallized that it was a "fuck you to teach you a lesson".
What really happened is that the "public perception" solidified before ppl had enough processing time, as you can tell by the fact that we've more or less completely decoded it by now (so much for "incomprehensible") and that when you get it what happens is that instrumentality was undone (so not 100% bleak either); Satisfaction, of course, will always remain a subjective quality
Like this line from shizo/parano for example:
"Right. To those on the outside, it looks like an illusion, but when it comes down to it I believe that happiness itself is an illusion. Human beings cannot escape from their solitude. All they can do is forget it. At that moment [of forgetfulness], they will be happy. That’s my recent conclusion. In order [to forget], you can watch anime, or sleep with a girl, and if you can escape from your loneliness while doing it, then perhaps you will be happy. If, when I get totally drunk, I feel like I am not alone, that’s an illusion, but it’s happiness."
That sounds less to me like "get off your butt leave behind your illusions & go find your ~real~ happiness" as it is a melancholy meditation on the fundamental human experience, ones own experience. Much of what ppl point at as "teaching ppl a lesson" is really a reflection of self doubt; I don't think the critical voice in the heads of the characters has to be taken for the truth, it's just a depiction of a feeling.
Where does meaning come from? If you put away cultural connections and the like you can arrive at the conclusion that it's just what ppl themselves attach meaning to. Yu can use the self knowledge to not be ruled by things you can't have or make you unhappy, but you'll still be assigning meaning to thinks yourself cause that is the only way to feel meaning.
So I don't see it as a story of "growth" as it is one of self-awareness/self-knowledge and Nietzschean Amor Fati. It's not linear; It's very, very circular.
We have yet to see how Rebuild ends but I don't think either of the existing two endings ended in "change".
The breakthrough realization in EoTV was more like a) You also have good & neutral traits & life experiences (that's what the Au sequence is; Shinji's life isn't all pleasant slice of life stuff, but pleasant slice of life experiences are a part of it, it's not all horror either) and b) you don't have to judge yourself
EoE if anything goes further like it explicitly ends with that scene where Shinji floats towards the surface after his parting from Yui & reflects on how he will probably continue to ask himself all these questions & have the same ponderings & even the same conclusions over and over again, fear & pAin included, and the moment the first other person demands that's exactly what happens.
Shinji winds up in the place that he started; what he gained is awareness, deliberateness. He's here now because he chose it, not because he is a helpless plaything of outside forces, as he used to view it earlier.
So that things end tragically with Kaworu that doesn't mean it was "wrong" to be with him in the first place (I mean just look at the post Q Ogata interview where she interprets his presence as "even if all goes wrong you can still form new bonds"); It just means that tragic endings to nice things happen & must be dealt with; & Shinji as someone with a rather preoccupied attachment style is of course overly concerned with good things ending to the point of avoiding or fearing them, but there is no ultimate permanence to them that you can grasp.
We are told explicitly directly 100% to your face that Kaworu (& Rei) represent hope, communication & words of affirmation & for years ppl have just ignored it despite how unambiguous & blatant it is. Ppl sometimes liking you & wanting to be your friend is not unrealistic or coddling, believe me it happens, sometimes, for a while.
Like Shinji says, it's a prayer, a hope, something that won't last forever - but so is all happiness. There is no happiness out there that is "realler" or less impermanent. But it's happiness; It's the reason he goes back.