Not the same person. That one was much less kingly.

but this one is in "The Last Kingdom"

Yes!

Æthelstan was a fairly common name among the anglo-saxons at the time. The "Æthel-" prefix, really - meaning "noble" - was common among both boys and girls.

I am unaware of the culture around non-binary people at the time and can't comment as to the popularity of their preferred naming conventions.

To the prefix, it survives widely in Germanic languages to this day in newer forms.

In Norwegian for example, "edel" and "adel" means noble - the former used for objects (a gemstone is an "edelstein" - noble stone; a noble gas is an "edelgass") while the latter refers to the nobility. You'll find one or both or variations in every (I think; certainly most) Germanic language.

We still have names derived from Æthel as well, e.g Ethel, Albert, Adele, Adolf, and others.

What does your second paragraph have to do with this discussion?

I’m not sure how people make such confident pronouncements about the 10th century (a great many things will have happened that long ago without any surviving historical record), but there is some evidence of negative attitudes towards gender-nonconforming people at the time that are depressingly similar to those you’ll find on certain internet fora today: https://en.m.wikipedia.org/wiki/B%C3%A6ddel_and_b%C3%A6dling

Oh my, you're easily triggered into parading your ignorance and intolerance. You should see a therapist about all that.

That’s a lot of extreme words for my simple comment. Lots of projection in your reply, such senseless and “triggered” commentary is actually the sort of thing a therapist could help you with.