In the whole of the Bhagavad Gita, actually Krishna uses the name Partha for Arjuna 38 times. He is pointing out to Arjuna who he is and what he is doing right now does not at all match what he is supposed to be doing. So, by mentioning his mother, he points out Pritha or Kunti, points out who is,. see if you read the original Mahabharata, the original verses, beautiful, just reading.