Approximately one in three children will live at least some portion of their childhood with a stepparent, according to recent statistics. These are individuals who will play an important and lasting role in children's lives.
However, from a legal standpoint, stepparents - even residential stepparents - generally have fewer rights than even legal guardians or foster parents. Still, in situations where a stepparent voluntarily receives a stepchild into his or her family and treated the child as a family member, he or she could be considered in loco parentis, meaning he or she assumes an obligation to maintain and support the child.
But absent a formal adoption, a stepparent who later separates from the child's biological parent and then seeks to establish visitation will face an uphill battle. It is absolutely possible, particularly if the child lived with the stepparent and the relationship was long-term. However, it's not an automatic right. If a biological parent opposes, the matter will have to be addressed in family court.