Not necessarily. There are male descendants from the late Shah's half brothers who were left out of the succession because their mothers were from the previous Qajar dynasty. Since Iran is no longer a monarchy I would think the head of the house could change that if he really wanted to.

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: http://www.rezapahlavi.org/details_article.php?english&article=485
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: Very sad. He is the second of the last
: Shah's children to die in this way. It
: is utterly heartbreaking that Empress Farah
: or any parent should have to suffer such a
: sorrow.
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: On the broader issue of Iranian monarchism,
: this means that there is now very little
: prospect that there will be a male Pahlavi
: heir to the vacant throne in the next
: generation.
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: