Baha'u'llah had a total of four wives. His fourth marriage was to a woman named Jamālīyyih.
This marriage took place late in his life. Jamālīyyih was related to one of Baha'u'llah's followers, as she was the niece of his loyal follower Khadimullah.
Persons familiar with Baha'u'llah's affairs confirm that prior to marrying Jamālīyyih, he had married a woman named Gawhar in 1867, who bore him a daughter named Furúghiyyih. His other wives included Navvab, the mother of 'Abbas Efendi, and his cousin Mahd-i 'Ulya, whose eldest son was Mīrzā Muḥammad 'Alī.
(Extracted from Der Bahaismus: Weltreligion der Zukunft? : Geschichte, Lehre und Organisation in kritischer Anfrage (Studienbücher im Gespräch mit der Zeit) - Francesco-ficicchia)(Earl Elder's Notes published in his translation of Kitab-i-Aqdas)
https://bahai-library.com/provisionals/aqdas/aqdas147.notes.html
https://www.reddit.com/r/exbahai/comments/1gvx6th/help_further_sources_on_the_topic_of_bahaullahs/