I have been toying with the idea of a monster who preys on the insecurities of those who have never known their mothers. But while I was thinking of this concept I got to wonder how Harry wasn't able to see Thestrals until he had seen Cedric die because when he was a baby, he couldn't understand death.
What I wonder is how old is a baby before they understand that their mother is really their mother. This monster would mostly prey on children whose mothers died durin childbirth or in their early lives, or mothers who gave their children up. But children who had their mothers in their lives long enough to know that this person was their mother would be uneffected.
So, how old is a child when they first become aware of the role of their mother?