It is apparent from the Guardian’s writings that where Bahá’u’lláh
has expressed a law as between a man and a woman it applies, mutatis
mutandis, between a woman and a man unless the context should make this
impossible. For example, the text of the “Kitáb-i-Aqdas” forbids a man
to marry his father’s wife (i.e. his step-mother), and the Guardian has
indicated that likewise a woman is forbidden to marry her step-father….
(28 April 1974 to an individual believer) [29]