So, with the new Allies rules in, I am tempted to adding some Dark Eldar to my Eldar force. Having a Farseer orchestrating my craftworlders, I thought of having either a female Archon or other DE HQ be the sister of my (also female) Seer, by having gone down the path of the Outcast and eventually wound up in Commorragh. And then it occurred to me that I could have a third sister who by some quirck of fate became a Shadowseer. This would give me three very fluffy characters on the battlefield and represent all three (currently) playable non-FW Eldar factions (ie. Corsairs and Exodites notwithstanding).
The thing is, would it be possible for a Craftworld eldar to become a dark eldar or a harlequin at all? Or do they have to be born into those sects?