"So if they say to you, 'Look, he is in the wilderness,' do not go out. If they say, 'Look, he is in the inner rooms,' do not believe it. For as the lightning comes from the east and shines as far as the west, so will be the coming of the Son of Man. Wherever the corpse is, there the vultures will gather."
"Immediately after the tribulation of those days the sun will be darkened, and the moon will not give its light, and the stars will fall from heaven, and powers of the heavens will be shaken."
"Then will appear in heaven the sign of the Son of Man, and then all the tribes of the earth will mourn, and they will see the Son of Man coming on the clouds of heaven with power and great glory. And he will send out his angels with a loud trumpet call, and they will gather his elect from the four winds, from one end of heaven to the other."
"From the fig tree learn its lesson: as soon as its branch becomes tender and puts out its leaves, you know that summer is near. So also, when you see all these things, you know that he is near, at the very gates. Truly, I say to you, this generation will not pass away until all these things take place. Heaven and earth will pass away, but my words will not pass away."
The Claim: Jesus said this generation will not pass away until all these things have happened, yet the time of the 12 disciples and their children and their children's children have all passed away. Jesus falsely predicted the second coming of Christ.
The Explanation: This whole passage is about the second coming of Christ. In fact, Matthew chapter 24 is all about the end times. Now, the claim is that Jesus said in verse 34 that before this generation passes away, all the preceding things will happen. The problem with this claim is that verse 34 comes after verses 1-33.
So if we keep Matthew 24:1-34 in the order it's written, the claim should then be this: These things will happen (verses 1-33), and that will be the end of the generation. From a purely logical standpoint, the second coming of Christ has not taken place yet, therefore we're not at the end of this generation, and there is no contradiction here.
Extra: This does bring up the question of what Jesus means by the phrase "this generation." What does "this generation" mean? It doesn't have to be 50-100 years of how we would think of a generation within our family. Generation in this sense could just be referring to a period of time that classifies an era. Let's take the Middle Ages for example, which is the time period from about 500 until 1500, which is roughly 1,000 years, not 50-100 years.
We don't know how long the generation Jesus was talking about will be. In fact, Jesus warns of false prophets in Matthew 24:4-5, where people falsely claim to be Jesus. Jesus also states in Matthew 24:36 that no one but God knows the exact date and time that these events will take place.