A new study reveals that parents might have a favorite child.

According to a recent study published by the American Psychological Association, birth order, gender, even a child’s temperament may determine a parent’s preferential treatment.

In some cases, the study found parents tend to give older siblings more freedom, which means the less favored siblings could have lower self-worth and problem behaviors.

However, the study finds more serious effects for children not favored by their parent, including struggling with behavior, mental health, academic success, and family relationships, especially among other siblings. If you feel like your sibling has been favored, that may create some animosity and resentment between you and your sibling. And later on, that can be seen in adult relationships as well.