Posted by: @col-klink

Is it possible that Polly's sister could be the mother or grandmother of the Pevensies? I don't love that idea and I know Fantasia has gone on record as being sick of storytellers making everyone related to everyone else these days.

I know I shared this somewhere recently, but Lewis genuinely did have the idea originally of making the Professor a relative of the main child characters in what became LWW. In a very early draft of the opening paragraph — in which he names the children as Ann, Martin, Rose and Peter — we're told that, because of the air raids, they were "sent to stay with a relation of Mother's who was a very old Professor who lived by himself in the country." (That's quoted in Past Watchful Dragons by Walter Hooper, who notes that he found this paragraph written on the back of something else Lewis was writing at the time when he had the young evacuees staying in his own home, early on in the war.)

While that original idea didn't end up in the final version, I wouldn't necessarily object to the Pevensies being related to either Digory or Polly. I don't know that it would enhance the story in any way, but I don't think it would ruin it either.

As for whether it's possible that one of Polly's sisters could be the mother or grandmother of the Pevensies, we could make some calculations based on the Narnia timeline that Lewis wrote up after finishing writing the Chronicles — bearing in mind that a) it's not always consistent with information given in the books themselves, and b) there's no telling whether or not this Netflix series (if it gets past the first film) will follow the same general pattern but putting all the this-world dates 55 years later than the originals.

Anyway, here goes...

First thing to note is that there is, in the timeline, a 40-year gap between MN and LWW. (This causes a significant problem with Digory's age — if it's taken as correct, he is only 52 at the time when the Pevensie children are staying at his house, which doesn't sound like him being a "very old Professor" at all. It's possible that an adaptation could increase the time gap between these two stories, especially if they decide to set LWW closer to the present day — perhaps in 2015 or even 2025 — instead of in 1995, as it would be if we add 40 years to the setting of 1955 for MN.)

According to the timeline, Polly is 11 years old at the time of the events of MN. If the three sisters she now reportedly has are all older than Polly, the oldest of them could easily be about 10 years older — 21 or so. That is old enough for her to be married and perhaps to have recently had a baby, or to be pregnant at the time of this story, or at least to be hoping to have children in the near future.

Also according to the timeline, Peter, the oldest Pevensie sibling, is born 27 years after the events of MN.

So if Polly's oldest sister has a new baby at the time of MN, or within the next few years, there's definitely enough time for that child to grow up and become the mother or father of Peter, and then of the other three Pevensie children.

(Having one of Polly's sisters as the mother of the Pevensies would be more difficult, if we're to stick with that 27-year gap before Peter is born, especially if Polly's sisters are all older. Polly's youngest older sister would have to be a year older than Polly at the very least, and if she's 12 or 13 at the time of MN, she would be 39 or 40 when Peter is born, and he's the oldest of four, which is... pushing it a bit, from the standpoint of female biology!!! But if Polly has a younger sister, it might be possible. I get the impression all the sisters are going to be older, though, which makes the "grandmother" scenario more likely, if this happens at all.)

There is — and this IS canonical — also the significant fact that in The Last Battle, we discover that the Pevensies and Jill and Eustace refer to Polly as "Aunt Polly" rather than as "Miss Plummer". Eustace explains that "She isn't really our aunt" — but what if she is the great-aunt of the Pevensies, and so they call her Aunt Polly*, and the two younger Friends of Narnia do the same? (Eustace is a cousin of the Pevensies, but he could be related to them on the other side of their family and therefore not be a relative of Polly's.)

We don't know if any of this is going to happen, of course, but it's an intriguing thought, and it would mean there is some point to Polly having siblings, after all... 

* It isn't unknown for great-aunts and uncles not to be called by the "Great-" tag. My own two legendary great-aunts (RIP both) insisted on us calling them Auntie Marj and Auntie Raie, and their respective husbands were Uncle Harold and Uncle Reg — because, as Auntie Raie put it, being called "Great-Auntie" made her feel too old!! I can definitely imagine Polly Plummer having the same attitude.