Yes, there is plenty of evidence that the twelve disciples were real people. In fact, no one who knows the evidence can seriously entertain the thought that these men were not real people. We have evidence from both Christian and non-Christian sources that the apostles were real people (I am assuming that by the 12 disciples you mean the 12 apostles). I was watching a video one time by Bart Ehrman, who is an atheist, but also one of the top scholars about things related to the Bible. A fellow atheist who was not well informed tried to tell Ehrman that he did not believe that Paul existed. Ehrman rebuked the man for making atheism look foolish. No serious person could claim that Paul did not exist. It would be like claiming that Cicero did not exist. This is crazy thinking.
We have the evidence from Josephus who tells us about the martyrdom of James, the brother of Jesus, who was the leader of the Jerusalem church. Josephus also relates the execution of the apostle James. We also have the evidence of the early church writers. The first important church historian, Eusebius, wrote in the early fourth century. He tells about all twelve of the apostles, plus Paul, relating where each ministered and how they died. Eusebius quotes his sources, such as second century historian Papias and Irenaeus and other Christian writers. The reliability of Eusebius varies somewhat, but he was a careful scholar and he quoted his sources. Some of the things he tells us about what happened to the twelve may be inaccurate, but what cannot be wrong is that there were twelve apostles. There is no way someone like Eusebius could have gotten the number of apostles wrong. Irenaeus, writing in the second century, tells us that he learned under Polycarp who knew the apostle John personally. Is it possible that Irenaeus got this wrong? I do not think so. If we go back to such books as the Didache and the Letter of Clement to the Romans, both written around the turn of the first century, that there were twelve apostles was assumed. This had been the tradition of the Christian church from the beginning of its existence. Is there any possible motivation for the church to make up the existence of twelve apostles? I cannot think of any.
The Didache, a very early Christian catechism dates from the very late first century. When it was written, some who had known the apostles were still alive, although they would have been quite old. The Didache is also known as “The Lord’s Teaching Through the Twelve Apostles.” The unknown writer of the Didache assumes that there were twelve apostles because it was common knowledge that there were twelve apostles. The people who knew Jesus personally would have known how many apostles there were. It is irrational to believe that there were not twelve apostles of Jesus because every account of Christianity is unanimous on this account, including even Josephus who was not a friend of Christianity.