“Often the child is trying to get the attention of the parent who is rejecting them — the more you push a kid away, the more he will come at you,” she said. “So if you see a kid coming at a parent, being aggressive or being clingy or needy or overly attention-seeking, often the parent doesn’t like the kid that much, or the kid perceives it.” She may ask the parent what that child’s behavior evokes; which other family member does it make you think of; what possible future does it make you imagine? Often, she says, the parent is aware of feeling strained toward that child, and feels terribly guilty about it; finding ways to enjoy spending time together can help them both.

Years ago I read a novel — someone please tell me what it was — in which a mother secretly and privately assured each of her children, don’t tell the others, but you have always been my favorite. I liked that system, and, as a mother, I think I could do it with perfect sincerity — one on one with each of my three children, I think I could say it and it would be true.

Ellen Weber Libby, a clinical psychologist and author of “The Favorite Child,” said some families have a shifting favoritism, where different children hold the advantage from day to day or week to week. That kind of rotation, she said, yields a healthy, normal competitiveness. Ask the children, she says, and they will tell you. “The people who don’t know are usually the parents, who live in denial because there’s a myth that to have a favorite child is bad.”