When the Lord showed Thomas his wounds to prove that He had risen from the dead, He said “Because you have seen me you have believed. Blessed are they who have not seen and yet have believed” (John 20:24-29). As I understand, this is why The Church has such a special relationship with God, we believe by faith alone. It is clear that the disciples started the Church. But, since it seems, that at least of part of the disciples’ faith is due to the fact that they had seen the Lord, his miracles, and his resurrection, does that mean that they (or anyone who saw Jesus during his ministry) are not part of the Church?
I don’t believe the Lord’s words in John 20:29 were meant to disqualify any of His followers from being part of the Church. I think He was criticizing Thomas for his skepticism. A careful reading of the Gospel accounts shows that none of the disciples truly understood His teaching on His resurrection until after the fact. Mark 9:31-32 is one example;
He said to them, “The Son of Man is going to be delivered into the hands of men. They will kill him, and after three days he will rise.” But they did not understand what he meant and were afraid to ask him about it.
Therefore I believe the disciples and other followers of Jesus who were alive at the time and believed in His death and resurrection can be considered as part of the Church.