Baha'u'llah's second and third wives, as well as their children, became the covenant-breakers.

The second wife of Bahá'u'lláh, whom He married in Tihran in 1849, was Fatimih Khanum, usually referred to as Mahd-i-'Ulya. She was a cousin of Bahá'u'lláh and gave birth to six children, of whom four survived. They were one daughter, Samadiyyih, and three sons, Muhammad-'Ali, Diya'u'llah and Badi'u'llah. These four, along with their mother, violated the Covenant of Bahá'u'lláh. Mahd-i-'Ulya died in 1904.

The third wife, Gawhar Khanum, was not known by any other title. The dates of her birth, marriage and death are not known. Her marriage took place some time in Baghdad before the declaration of Bahá'u'lláh's mission. While Navvab and Mahd-i-'Ulya travelled with Him in all His exiles, Gawhar Khanum remained in Baghdad with her brother, Mirza Mihdiy-i-Kashani. For some years she was among the Bahá'í refugees in Mosul[34] and later went to 'Akka at Bahá'u'lláh's instruction. She gave birth to one daughter, Furughiyyih; mother and daughter both became Covenant-breakers after the passing of Bahá'u'lláh.

(The Child of the Covenant: A Study Guide to the Will and Testament of 'Abdu'l-Baha by Adib Taherzadeh)

https://bahai-library.com/taherzadeh_child_covenant&chapter=all