In Matthew 10:2-4 the disciples are listed in pairs (presumably parallel to the "two by two" of Mark 6:7):
The names of the twelve apostles are these: first, Simon, who is called Peter, and Andrew his brother; James the son of Zebedee, and John his brother; Philip and Bartholomew; Thomas and Matthew the tax collector; James the son of Alphaeus, and Thaddaeus; Simon the Zealot, and Judas Iscariot, who betrayed him
The pairing of brothers (Simon and Andrew; James and John) is obvious. Based on his surname of Iscariot, it has been speculated that Judas might have been a Zealot. If that speculation is true, half of the pairings have an obvious choose-your-lab-partner character. Are there any additional indications that the other pairings were of this nature or that the pairings overall were not arbitrary?