I think you are right, I think he was a child who was already starved for attention (the fourth boy), being left to his own resources to have his needs met and find his way...and so when he heard this, I think it was like, "aha, that's why she doesn't love me, give me the attention I crave, I can't please her or get what I want from her..."
So yes, I think there must be fertile ground for something like that to take root.
