In Tagore's "The Postmaster," how did the postmaster's family become very much a part of Ratan's life?

The postmaster's family became a part of Ratan's life as a way to become closer to him as well as to experience family life.
As the postmaster stays on in Ulapur, his need for companionship increases. Being a new transplant to the village, he knows no one.  The only bond he forges is with Ratan.  Being an orphan, Ratan has no connection with anyone.
However, upon befriending the postmaster, Ratan experiences the joys of human contact.  It becomes a new world to her.  She waits on the postmaster, and tends to his every need.  As their relationship increases, she "would sit outside waiting" for him to call out to her." Ratan fully immerses herself in his world.  She recognizes this as a way to strengthen their bond. This is why his family becomes very important to her.  When he would "call up memories of his own home" and of the family he missed so much, Ratan would facilitate conversation.  By "recalling them aloud in the presence of the simple little girl," the postmaster's and Ratan's connection became stronger.  She ended up appropriating them as her own family so that he would feel more comfortable with her. This is why she would "allude to his people as mother, brother, and sister, as if she had known them all her life." In making his family her own, Ratan is able to increase her bond with the postmaster.
However, there is something a bit more melancholy behind Ratan's adoption of his family as her own.  Tagore is deliberate when he writes, "In fact, she had a complete picture of each one of them painted in her little heart." Ratan is unable to form pictures about her biological family.  The orphan knows little of her own past.  Yet, through the postmaster's retelling of his own family, she sees and experiences familial love.  In making his family her own, Ratan is able to go back into her past.  She can experience what she was unable to experience when she was a child.  There is something poignant about an orphan finding a family wherever it might exist.  In Ratan's "little heart" is this possibility of having a family.  It might be his, but through immersing herself in it, she recaptures a moment when she feels what it's like to have a "mother, brother, and sister."  In this way, Ratan acquires even more sadness to her characterization.