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However you like, make it that Juana 'la Beltraneja' succeeds her father when he dies.

Rules:

1) Isabel of Castile is not allowed to be killed in order to make this happen.
2) Any of Juana's ill-fated husbands/husbands-to-be may survive though - the king of Navarre, the duke of Guyenne or the duke of Lorraine, etc - (mostly because I find the idea of her marrying her uncle (Affonso of Portugal or Alfonso of Castile) gross (I know it was the done thing, that doesn't make it less gross, marrying her cousin, Joao II is fine though)) in order to get this done.
3) No ASB fairies: aside from another pregnancy in the same year as Juana (a son in December 1462), you can't go giving her parents a raft of children in order to make Juana's legitimacy more believable, for instance).
4) For the sake of the challenge, we are assuming that Juana is as legitimate as Isabel is (especially since no one has anything more than rumors "implying" that she wasn't).

Have at it, guys and girls.
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