No, he was "called a brother" and because he was living in unrepentant sin, they were not really a brother. We were to treat them as if they were not saved because they are acting like an unsaved person. He wa "called" a brother, but wasn't really one. He was not saved.
"I wrote to you in my letter not to associate with sexually immoral people—not at all meaning the sexually immoral of this world, or the greedy and swindlers, or idolaters, since then you would need to go out of the world. But now I am writing to you not to associate with anyone who bears the name of brother if he is guilty of sexual immorality or greed, or is an idolater, reviler, drunkard, or swindler—not even to eat with such a one. For what have I to do with judging outsiders? Is it not those inside the church whom you are to judge? God judges those outside. “Purge the evil person from among you.”
(1 Corinthians 5:9-13 ESV)
Repentance is the difference.
First, it's a very nieve thing to think that everyone that's a member of a church is truly born again. Church discipline is to restore believers to repentance. If they don't repent, we are to treat them as unsaved. This person was not saved. Paul was very clear in his wording. He says "called a brother" or "bears the name brother." This alone is a clue that we are dealing with someone that isn't really a brother but is just "called" one. In the end, it says they are an "evil person." We are to "purge" them from among us because they are not a believer but really an outsider.
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