Male cohabiting partners (MCPs) in low-income urban Black single mother families may represent an extreme case of stepfathers who have been characterized as “polite strangers” in the household. The purpose of this study was twofold: To examine who serves as a coparent in these families; and to determine if identification of a coparent in addition to or instead of the MCP would be associated with the level of MCP involvement in the family. Participants were 121 mothers and adolescents from cohabiting families. The MCP was identified as a coparent in 75 % of the families, an additional coparent was identified in only 30 % of the families, and, when the MCP did not serve as a coparent, another individual was identified in this role in only 24 % of the families. The identification of an MCP as a coparent was associated with higher levels of MCP childrearing activities, coparenting support provided by the MCP, and relationship quality with the mother relative to no coparent being identified. The identification of another coparent in addition to the MCP was not associated with changes in the higher levels of family involvement found when the MCP was a coparent. The importance of a male cohabiting partner for coparenting of an adolescent is emphasized in the discussion of the findings.