It's possible, though less likely. Whatever sphere was chosen would have to clearly relate to the Maiden, the Mother, or the Crone with a good justification as to exactly why it fits. All of Amaranthe's followers serve her through one of those Aspects, so the important thing is to be able to tie that in somehow.

Alright, well. Say a sphere Earth. I was reading your other things, it would technically relate to all three. A hope to nurture the earth and such that he/she technically worships. I suppose that would be more of the Mother than anything else, but you see what I mean? Probably work or not? Able to say or no?

It would be up to you to devise a role/background that is influenced by one of the Aspects in a way that reflects your Sphere. I know which Aspect *I* would pick for earth, but that doesn't mean you should pick the same one.

It all comes down to how well you roleplay it. (Or at least how well you roleplay it in my estimation).