Originally Posted by
rutog98
Actually, Morrison followed the continuity that the Phoenix Force was its own sentient entity that possesses people. Hence, when Jean confronted Emma over her psychic affair with Scott, she knocked Scott out of the room and then told Emma, "Now its just you, me, and the Phoenix."
Also, in Excalibur, it was established that there have been tons of hosts for the PF.
When the PF first came into being in canon, Marvel had not really worked out all the bugs on what the Phoenix Force was. Originally, it was supposed to be something tethered only to Jean and her lineage, however, by Excalibur, they settled on it being a sentient cosmic abstract entity that has possessed many people since the creation of the universe. This has been the prevailing story of the PF for the overwhelming majority of its existence as a Marvel Comics character. Morrison simply built on that and AvX made it so that anybody can now serve as host to the PF.