maybe (IMO) they were the Seelie and Unseelie court .. during the age of Ice.
not anymore...
1) they are 'best enemy'
2) while in the pédia, the Seelie queen loves her 'sister' queen, the Unseelie Queen hates her guts and is much more aggressive.
i can really imagine that with the age of rebirth, seeing winter dwindle and becoming shorter, foreseeing an even shorter periode of reign for herself, hating the peaceful and dumb decision of her fellow queen, the Unseelie Queen and her followers secessionned from the ljosalfar during a very bloody revolution (or a failed coup atempt). (only bloody events can cause people of a same race to be worst ennemy).
Maybe they were the Seelie and Unseelie court, but now.. century laters, they are only two different peoples, with different technologies and cultural aspects, their racial linkonly apparent through the pedia entries and the elven promotion.
EDIT : correction
this implyes : that I was mislead by my imagination, (separation of the two court occuring during age of ice and not after and not totally for the reason I thought) but : 1) they are two very different peoples ; 2) there is effectively bad blood between the two faces of the elven nation.