Peace Light,
Iblis lived among the Angels but he was not an angel himself. Allah says in the Quran:
Behold! We said to the angels, "Bow down to Adam": They bowed down except Iblis. He was one of the Jinns, and he broke the Command of his Lord. [The Noble Qur'an 18 :50].
As you can see, he is of the Jinn and not an angel!