@LadyRunic I'm so sorry you're not feeling well. *brings you fans and cold drinks*
Oh, and I never said sprites don't exist in Winter, but I'm pretty sure there are fewer of them. ^.^;; Pesky buggers must annoy the current Queen enough that she killed those that bothered her and the others most likely started going to Fall and Spring. Not all, but enough to make a difference.
As for half-fae...this is confusing still. Changed humans are seasonborn, and they're full fey. Their genes are dominant over those of humans, or were, so while they're weaker they wouldn't be able to breed with a human either. If the mother was a seasonborn, how was she in the mortal realm to start with? Or was she turned but then the kelpie lost interest or something and chucked her in the mortal realm to die? And how can the powers of a full fey be dormant? It makes sense for a fey that becomes a changeling, possibly, but not otherwise.
As for Maxwell, we now need to sort out how changelings work. Are they still considered fey, and thus unable to have children with humans? Or are they considered humans and so their descendants have latent powers that can be awoken by some ritual or artifact or something? My preference is for the latter, and I feel the latent fey blood might still have a very subtle effect for story reasons (such as the family's affinity for medicine and the aversion to direct promises).
I'm really not sure how half-fey contradicts seasonborn, actually, though it might be secret lore regarding seasonborn -- or regarding somethign else entirely. Hope we can get it sorted out!