ではと - is this a particle?


> それは、玉座に繋がれた真祖の姫ではなかった。  
>  彼女は今でもあの間に繋がれたままである。  
>  これは彼女の内面に潜む、彼女と融け合う事を待っている彼女に他ならない。  
>  「はじめましてブリュンスタッド。  
>  こうしてお話をする機会が回ってくるとは思いませんでした。  
>  **なにしろ貴方があの様子では、受け継ぐのは姉君ではと危惧していたものですから」**
>
> This isn't the princess of the true ancestor chained to the throne.  
>  She is still chained there. This is what is dwelling inside her and is
> waiting to melt with her. Honored to meet you Brunesteid.  
>  I did not think I could meet you like this and talk to you.  
>  At any rate if you are in that condition, if it's that sister I doubt that
> inheriting is possible.

Or since he was speaking about waiting to melt I think

> At any rate if you are in that condition, I doubt you can take over your
> sister.

I think:  
ではと  
では=Used before a negative consequence or something that is not favourable  
と=Quoting particle

I looked for definitions of the words and found that:  
受け継ぐ:前の人の仕事などを引き継ぐ。また，人の性質や志などを引き継ぐ。継承する  
姉君:姉を敬っていう語。姉上。  
危惧:うまくいかないのではないかと，あやぶむこと。危懼

I understand these 3 definitions and I tried my best to understand how the
grammar works in the bold sentence.

Edit: I thought 姉君 could be used when addressing older girls  
so

> At any rate if you are in that condition, i doubt that for you it's possible




> 「受け継ぐのは姉君では」と危惧していた  
>  I was worrying that the person who succeeds might be your older sister
> (instead of you, Brunesteid).

  * 受け継ぐの: "the one who succeeds" (i.e., the successor)
  * は: topic marker
  * 姉君: (honorific) "older sister"
  * では: =ではないか; "Isn't it that ～?", "I guess ～?", "perhaps"
  * と: quotative particle
  * 危惧していた: "I was worrying" (not "I doubt")

Here's more examples:

>   * 殺したのはお前だ。 It's you who killed (someone).
>   * ケーキを食べたのはお父さんでは? The one who ate the cake is Dad, I guess?
>   * 悪いのは誰だ!? Who is to blame!?
>   * 見えないのでは。 Perhaps you can't see it.
>   * うまくいかないのでは（ないか）。 I guess this won't go well.
>   * うまくいかないのでは（ないか）とあやぶむ to worry, thinking "this may not go well"
>

