Is pein the third Hokage son?

Answer 1

No, because the 3rd Hokage already has a son named Asuma Sarutobi (not I'm saying he couldn't have another son). Although, there are some rumors that Pein could be Naruto's long lost brother and he is the first son of the 4th Hokage!

Good guessPein could very well be the third hokage's son, but Pein is most notably Jiraiya's best pupil gone bad. How, and where you ask?

Pein was one of the many orphans in the rain village, and Jiraiya was there or just passing through and took at interest in Pein as well as several others, and taught them basic ninjutsu.

Pein later on killed the rain village's leader, Henzo, the same man who gave Jiraiya, as well as his teammates, the name sannin, having been able to hold his own against henzo, with no one else being able to do even that.

Once deidera blew himself up trying to kill level 2 Sasuke, Tobi almost died, but came back thanks to a special healing jutsu (that he doesn't mention) and takes charge just like madara uchiha, and orders pein to capture and rip the nine tailed fox from naruto, as itachi and kisame hoshigaki failed to do so.

However, just like with Itachi and Kisame's attempts, Jiraiya steps in the way, though he was fortunate with the first battle, as he loses an arm due to Pein's 6 paths of pain move, trying to keep pein from his newest pupil.

Personally, I think that jiraiya will die and naruto will have to avenge him (Jiraiya is like his stepfather) through defeating pein like sasuke avenging his lost family through the defeat/death of his bro, itachi.

jiraiya does die pein kills him,his 6 path body stab him 4 times in the stomach and cuts his throat,but before he dies he puts his mind in a toad and it travels to the leaf village and naruto cries and blames tsnade

I think Naruto will kill Pein.because he killed Kakashi and Jiriya. Real answer here Ok, so Jiraiya does die by Pein. Also, Pein couldn't have been the 3rd's son because Jiraiya as mentioned before found Pein and his friends during the 3rd Great Ninja War. Pein also known as Nagato, told Jiraiya that he and his 2 other friends were from the village hidden in the Rain.

Also from the "Good Guess" section:

Tobi is Uchiha Mardara. He says so himself after the battle of Saskue and Itatchi, Mardara reveals who he really is. ALSO, Mardara does not have a healing ability!!! His basic ninjustu is dimention teleportation, also as fast as the 4th Hokage but not quite faster. That is why he was able to get away.

Peins Parents are two amegakure ninja who where killed by some konoho ninja his parents where not Hiruzen Sarutobi or Minato Namikaze (the third and fourth hokage)