Board Thread:Questions and Answers/@comment-9205010-20140323083245/@comment-6532078-20140323124312

No, they probably can't be both. For example Sinbad stated in chapter 88 that in case Morgiana met Djinn before activating her Household, she could conquer Zagan's Dungeon. Also Leraje told Kouha that he's not a "Household Member material" and that's why she decided to be his Djinn, implying your answer.

Don't worry if it's written somewhere her, feel free to ask ;D