Sounds like extreme jealousy of a co-dependent child feeling abandoned due to the new child getting mother’s attention.
This is common when a mother dotes upon a child and then a newborn forces the mother to transfer all her attention away from the older child.
Thirteen is extreme age for this.
I encounter this often in my work when a mother has a second child that requires her attention when the older child has not gone through the terrible two’s. The terrible two’s are when a child creates separation from the mother and begins to develop a separate sense of self.
I have found in my research that this pattern often causes a fear of intimacy for the older child throughout life. This is very common in men who perpetually cheat on their relationships.
Apparently, in the case mentioned in the article, the helicopter mom never allowed the older child to develop a sense of self. Thus the intimacy of the co-dependency was violated by the appearance of the newborn.
This pattern is common in single parenting where no thather is present to balance the mother’s energy and it all focuses on the developing child. It is especially true when the mother is strong masculine and her energy causes the son to develop as her compliment, as feminine rather than having his own healthy self identity.
In my work, I search for the perceptual programming events that create personality and behavior problems later in a person’s life. The strongest perceptual programming events happen ehen the child is in the mother’s womb as a child in the womb cannot differentiate between the mother’s experiences and their own.
It’s easy to determine how the parents got along by reading the stored memories on the outer perimiter of the child’s soul, even though it may be 50 plus years later and the child is now grown.
For example, approximately 90% of the lesbians I worked with, the mother was angry at the father during pregnancy. I’ve worked with many. These stored memories in the soul are so emotionally strong it usually knocks the person off their feet when I touch the stored memory many feet from their physical body.
This unhealthy emotion is further exacerbated when the newborn is a girl and the older child is a feminine boy.