3 XBee !Star Network! (GPS,Arduino)

I have 3 XBee PRO S2C and 3 Arduino MEGA and 2 GPS GY-NEO 6MV2. I would like to transmit GPS datas from 2 Router XBee
(they are connected to arduino) to coordinator XBee (also connected to Arduino and PC). But I don't know how to
configure XBee's to receive 2 different GPS datas healthy.I want the GPS data to not get confused and get it right.
API mode or AT mode ? How could I configure 3 XBee like
STAR NETWORK ?