When men live with the children of their spouse or partner, only some respondents identify them as the stepfather. News Release, US Census Bureau As blended families become more common, the definition of fathering extends well beyond men\u2019s own biological or adopted children. There are 4 million men who live with the children of a spouse or partner, according to the Men\u2019s Fertility report out today. A subset of those men \u2014 1.8 million \u2014 do not live with biological or adopted children of their own. Men who live with younger children of their spouse\/partner are less likely to be identified as a stepfather Of those men, the majority \u2014 59.9 percent \u2014 are identified as a stepfather to one or more children in the household and 40.1 percent are not. Age Makes a Difference Men who live with younger children of their spouse\/partner are less likely to be identified as a stepfather: 43.8 percent of men living with children 0-5 years old and 54.7 percent of men living with children 6-11 years old. Identifying men as stepfathers is higher when children are older. Almost 65 percent of men who live with children of a spouse or partner who are aged 12-17 (and no biological or adopted children of their own), are identified as a stepfather. These data come from the Survey of Income and Program Participation, which collects detailed information about U.S. families\u2019 economic well-being, as well as complete fertility histories of adults. For information about how parent\/child relationships are determined in the SIPP, please see the subsection, "Measurement of Fatherhood in the SIPP" in the Men\u2019s Fertility report.