Who is referred to as the charioteer in the the short story 'My Beloved Charioteer' written by Shashi Deshpande?

In the short story written by Shashi Deshpande, the grandmother (Ajji), mother (Aarti) and a grandaughter (Priti) are the characters. Grandmother or Ajji narates her family's situation post the widowing of herself and her daughter. The story takes reference to the charioteer who leads the path to the passenger board the chariot. Its comparison to the characters in the story is not clear due to use of pronouns instead of names. Can anybody please answer who is referred to as the charioteer in the story?