You made me think. I am the oldest child, wife is youngest. Her middle child is a boy between two girls and we are not like what you describe but my son is, mine is a boy with an older brother and younger sister. He is the only one we never see. I miss him. We have talked and studied much about it but never came to an answer. I do know his mother made him a victim and he had a hard time growing up. I never got the chance to have the relationship with him I have with his siblings and I can't say why.