Research has suggested that having a biological connection does not necessarily impact on the way a father parents his children.
The study, which is published in the Journal of Marriage and Family, looked at the parenting skills of four groups of dads in relation to whether they were biologically related to the child or married to the child's mother.
It found that married social fathers - those that are not the biological parent of the kids - showed equivalent or higher quality parenting behaviors than married and cohabiting biological fathers.
Married and cohabiting biological fathers displayed relatively similar quality parenting, while married social fathers were shown to be more engaged with their kids and took on more shared parenting responsibility with the mother. This latter trait was the most notable difference between social and biological fathers.
The report's authors concluded: "On the whole, our findings suggest that marriage is a better predictor of parenting quality with regard to social fathers than biological fathers."
Many US families no longer follow the traditional pattern of two married parents plus their children, with gay parents, step families and other variations becoming increasingly common. This research shows that traditional is not necessarily always best.