There are two main reasons why the break-up of parents can affect kids negatively. The first is simply fewer resources. After a split, its hard to make the total family income cover the expenses of two households rather than one.

How does divorce affect a child mentally?

Research has documented that parental divorce/separation is associated with an increased risk for child and adolescent adjustment problems, including academic difficulties (e.g., lower grades and school dropout), disruptive behaviors (e.g., conduct and substance use problems), and depressed mood2.