They were a group of 12 leaders appointed as apostles by John.  These apostles first received their instruction from John.  Politics and selfish preferences provoked many arguments among John's disciples.  They anointed the sick with oil, a rite that Jesus' apostles refused to adopt.  Jesus saw to it that his apostles maintained good relations with John's apostles.  Jesus refused to participate in the joint conferences in which they discussed with his apostles.  They were finally won to the cause of Jesus.  They never knew why Jesus did not prevent John's death. 
See also: UB 135:9.1.