I have started to research into J.M.Barrie's life, and I have discovered that he was quite well off from the beginning, rather, he had a good education at three different Scottish Academy's. I also discovered that his mother favouritised his older brother, David. A quote from Wikipedia explains how issues with his mother may have been a psychological aspect to his creation of Peter Pan. "When he was 6 years old, David died two days before his 14th birthday in an ice-skating accident. This left his mother devastated, and Barrie tried to fill David's place in his mother's attentions, even wearing David's clothes and whistling in the manner that he did. One time Barrie entered her room, and heard her say 'Is that you?' 'I thought it was the dead boy she was speaking to,' wrote Barrie in his biographical account of his mother, Margaret Ogilvy (1896), 'and I said in a little lonely voice, "No, it's no' him, it's just me."' Barrie's mother found comfort in the fact that her dead son would remain a boy forever, never to grow up and leave her."
This, I believe, is a significant reason to why Barrie carries on the idea of 'motherhood' in Peter Pan; Peter Pan may be a symbol of him, who is searching for a mother, and Wendy may be the symbol of the embodiment of his mother or the ideal mother.
This comes back to Sigmund Freud's psychoanalystic theory of "The Oedipus" joint with Carl Jung's theory of the archetypes to do with the mother (anima). I'm going to try and go deeper with this concept in my own appropriation I think.