Regardless of how often we hear, “it doesn’t matter who raises a child as long as they are safe and loved,” the data reveals that being raised by both biological parents is one of the strongest predictors of whether or not a child will actually be safe and loved. But don’t take my word for it.  Listen to the experts:

First, research clearly demonstrates that family structure matters for children, and the family structure that helps children the most is a family headed by two biological parents in a low-conflict marriage. Children in single-parent families, children born to unmarried mothers, and children in stepfamilies or cohabiting relationships face higher risks of poor outcomes than do children in intact families headed by two biological parents. – Kristin Anderson Moore, Susan M. Jekielek and Carol Emig, “Marriage from a Child’s Perspective: How Does Family Structure Affect Children, and What Can We Do about It?”, Child Trends Research Brief, June 2002.

If we were asked to design a system for making sure that children’s basic needs were met, we would probably come up with something quite similar to the two-parent family ideal. Such a design, in theory, would not only ensure that children had access to the time and money of two adults, it would provide a system of checks and balances that promote quality parenting. The fact that both adults have a biological connection to the child would increase the likelihood that the parents would identify with the child and be willing to sacrifice for that child and it would reduce the likelihood that either parent would abuse the child. – Sara McLanahan, Growing up with a Single Parent: What Hurts, What Helps

Most scholars now agree that children raised by two biological parents in a stable marriage do better than children in other family forms across a wide range of outcomes.” –Brookings Institute

Unrelated Adults Are Less Protective, Invested, and Connected to Children

Decades of research on family structure (or simply googling “mother’s boyfriend”) reveals that it takes more than being in a romantic relationship with a child’s parent, to be a good parent to a child. It’s widely acknowledged that adults respond differently to children who are not biologically related to them.  They tend to be less invested, connected, and protective towards unrelated children.  This phenomenon is known as the “Cinderella Effect.” Children are more likely to be neglected and abused when living with an unrelated cohabiting adult, especially an unrelated male. Brad Wilcox summarizes the data from the Fourth National Incidence Study of Child Abuse and Neglect:

…children living with their mother and her boyfriend are about 11 times more likely to be sexually, physically, or emotionally abused than children living with their married biological parents. Likewise, children living with their mother and her boyfriend are six times more likely to be physically, emotionally, or educationally neglected than children living with their married biological parents. In other words, one of the most dangerous places for a child in America to find himself in is a home that includes an unrelated male boyfriend—especially when that boyfriend is left to care for a child by himself… The science tells us that children are not only more likely to thrive but are also more likely to simply survive when they are raised in an intact home headed by their married parents…

There are also risks to children who live with step mothers. Three Princeton economists found that children who live with a stepmother are likely to have less health care, less education and less money spent on their food than children raised by their biological mothers.

  • Among children over a year old, living with both biological parents, the health study found that 61 percent have had a medical checkup within the last year. But among those living with a stepmother and birth father, that number dropped to 46 percent — and of those whose biological mother was dead, only 35 percent had seen a doctor.
  • Of the children living with their biological parents, 74 percent wear seat belts almost all the time, compared with 63 percent of those living with a stepfather and biological mother and 52 percent of those living with a biological father and stepmother.
  • Families with a stepmother reported overall household food spending that was about 5 percent lower for each stepchild than in families in which both biological parents were present, the food study found.
  • In families in which women care for both their stepchildren and biological children, the biological child, on average, went to college for a year, while the average stepchild did not go to college.

In a recent study, “The Puzzle of Monogamous Marriage,” the authors write:

Much empirical work in monogamous societies indicates that higher degrees of relatedness among household members are associated with lower rates of abuse, neglect and homicide. Living in the same household with genetically unrelated adults is the single biggest risk factor for abuse, neglect and homicide of children. Stepmothers are 2.4 times more likely to kill their stepchildren than birthmothers, and children living with an unrelated parent are between 15 and 77 times more likely to die ‘accidentally’.

Another recent study revealed that children are healthier and more likely to grow up with a good education and to get a good job if their biological father is with them. But when a step father moved into a family home there are no benefits for the children.

[The report] said when single mothers were joined by the children’s biological father, then if the family stayed together, the children were as likely to do as well as children of the best-off stable families, those which were always headed by both a mother and father. But if a stepfather joins a family headed by a lone mother, then the children are likely to grow up with the same problems as children from families that continue to be led by a lone mother.

The well-understood risks posed to children who are under the care of a biological stranger is the very reason why adoptive parents rightly undergo scrutiny prior to, and supervision after, having a child placed with them.

Increased Risk of Traumatic Events, Emotional, Physical & Sexual Abuse 

A massive study conducted by the Center for Disease Control measured the incidence of traumatic event for children living with both biological parents compared to children living with one or neither biological parents.  It’s findings: “of the children surveyed, 70 percent of those in a home with both biological parents had experienced none of the identified traumatic circumstances (living with someone who is mentally ill or suicidal, living with someone who had an alcohol or drug problem, witnessing violence in the household, etc) while only 20 percent with one or no biological parent in the home experienced none of the circumstances. The authors of the study say they looked at these nine adverse events because research has shown children are likely to experience long-term effects—including poor adult health, risk of illicit drug abuse, and risk of suicide—from traumatic events experienced at an early age.” The graph below reflects data from the National Incidence Study (Number 4) in 2010, a periodic surveillance of child physical, sexual and emotional abuse. It is clear that the rates of abuse are far lower with “married biological parents” (the only category where both parents are the child’s biological parents) than any other category. Below are similar findings from the US Centers for Disease Control, study titled “Family Structure and Children’s Health” based on the National Health Interview Survey. Protecting and advocating for children involves understanding how biological connection in the parent-child relationship impacts child well-being.  The statistical reality is that there are significant benefits and protections when a child is raised by both biological parents.  No other family structure approximates the benefits to children who are raised- not just by two loving adults, nor by just a married man and woman, nor even by their own unmarried parents- but by their married biological parents.