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John the Baptist had older parents, Zechariah and Elizabeth. He is believed to have been orphaned at a young age and was fostered by Essene monks in a desert monastery. That is why he was strange in his behavior of sack cloth garments and wilderness food. This is all conjecture but it would explain a lot.
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If by "line" you mean which of the Twelve Tribes of Israel, John was a Levite. This is how Luke introduces John's parents:
Luke 1:5 - There was in the days of Herod, the king of Judea, a certain priest named Zacharias, of the division of Abijah. His wife was of the daughters of Aaron, and her name was Elizabeth.
Only Levites were priests, and Elizabeth is also identified as a "daughter of Aaron," meaning she, too, was a Levite.
Luke's Gospel says that Zechariah the priest was the father of John the Baptist, indicating that John was born in Jerusalem and that his mother was a cousin of Mary, mother of Jesus. The other gospels do not support this statement, and John's Gospel suggests that Jesus and John were strangers.
Uta Ranke-Heinemann (Putting Away Childish Things) believes that Zechariah and Elizabeth were literary creations and that the Lucan story of the birth of John was fictional. Among other things, a parallel can be seen between Luke's story of the birth of John and the Old Testament story of the birth of Isaac.
Other groups also claim John the Baptist as their own, suggesting that he was a very popular preacher in first-century Palestine. The Mandaeans, of whom a remnant still exists in southern Iraq, claim that John was one of the founders of their religion and that he was never really associated with Jesus.
The different claims in each of the New Testament gospels point to the likelihood that John's teachings competed with those of Jesus, and the early Christian Church needed to neutralise this threat to their faith. Unable to condemn John as easily as certain others were condemned, the author of the first gospel (Mark's Gospel) portrayed John the Baptist instead as heralding the coming of Jesus and as saying that he himself was unworthy to loosen the straps of Jesus' sandals. John was executed by Herod Antipas in 35-36 CE, but such a late date would be incongruous for someone whose principal role was said to be to preach the coming of Jesus, so his death was moved to the very beginning of the mission of Jesus.
The story in Luke of John's origins is regarded by many scholars as fictional, and the gospel story that links John to Jesus is probably a late invention, leaving us with very little historical information about him, other than Josephus' account of his death. We do not really know where he came from.