TTWSYF: to respond to your post...
Irenaeus of Lyons: did not know apostles, he wrote around 175CE; he's only repeating what he heard from Polycarp, who he knew when he was a boy
Justin Martyr: did not know apostles, he only repeats what he's been taught and read in the "memoirs of the apostles," i.e., canonical gospels; wrote around 150CE
Ignatius: fake letters, probably forged by Polycarp himself
Clement of Rome: in 1 Clement he never claims to have known apostles, he speaks of them at a distance
But even if these people knew apostles, that would only make their claims early, not true. Early claims could still be lies. Within days of 911, I was being shown pictures of Satan's face in the smoke of the twin towers, and shown pictures of "missiles" the US had supposedly fired at the planes.
Early does not equal true.