The two leaders were expelled by PDP president Mehbooba Mufti on Tuesday on the recommendation of a disciplinary committee headed by party vice-president Abdul Rehman Veeri.
Bukhari and Hussain joined the National Conference at the simple function at party president Farooq Abdullah's residence, where vice-president Omar Abdullah was also present.
Bukhari, a two-time MLA from Sangrama, is the elder brother of slain journalist Shujaat Bukhari, who was shot dead along with two security officers by Lashkar-e-Taiba (LeT) terrorists in June.
He was the law minister in the PDP-BJP coalition government, headed by the late Mufti Mohammad Sayeed. He was made the revenue, relief and rehabilitation minister when the government was led by Mehbooba Mufti.
Hussain, a former MLA from Shangus constituency, was a minister during the PDP-Congress coalition government in 2002. He did not contest elections after 2002 and was appointed as the vice-chairman of the waqf board by the PDP-BJP government.
(With inputs from agencies.)