Neytiri and Sylwanin - twins?

[Ashen Key]

I was reading through a PDF of the Pandorapedia from the blu-ray, I came across the section on Na'vi families. I mentioned that the Na'vi women tend to have between one and ten children, often widely spaced apart.

Now, I do know that the implication is that Sylwanin is older, but in the photograph that Jake is holding when asking about the school (which makes it seem a deliberate prop-choice)



the girl between Grace and Neytiri looks roughly the same age as Neytiri. My own private theory is that Neytiri and Sylwanin are fraternal twins (which in turn makes an interesting mirror with Jake and Tommy, with Neytiri being the next-shaman while Sylwanin was the really out-there, physical warrior), but I was wondering what other people's thoughts were.