Are there any stories of anyone in the Equestria Girls world adopting children? I’d like to see stories of Sunset Shimmer adopting a child or Principal Celestia ......or one of the sirens, (I could see Adagio or Sonata being a mother.)

there are

There is this one where Sunset adopts a kid. I think it's, "To be a sister". Also, "Winter stars of Christmas".

And there are a lot of stories where Principal Celestia adopting Sunset. Not exactly what you are looking for. I wrote one myself if you are interested.

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i know the first one you said it is really called "A tale of a loving sister" by "GoebelTron"

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Oh yes that one, sorry

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There's one called The Rainbow and The Comet by RNBW.

It's a good story to read.