Mirza Yahya pretended to be the re-incarnation of Quddús, claimed prophethood

It is in Adrianople that Mı́rzá Yaḥyá, Bahá’u’lláh’s half-brother and the one who pretended to be the re-incarnation of Quddús, openly unleashed his rebellion against Bahá’u’lláh after years of covert work sowing discord among the community of Bábı́s—now Bahá’ı́s. Mı́rzá Yaḥyá also claimed the station of prophethood and to be the successor of the Báb. He was summoned to appear in a mosque and to raise his allegations in front of Bahá’u’lláh in public, but he failed to appear. As a result of his rebellion and claims, Bahá’u’lláh severed all ties and communication with this impostor and moved His residence to another location in Adrianople.

(Quddús - The First in Rank by Boris Handal)

https://bahai-library.com/pdf/h/handal_quddus_first_rank.pdf