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Over One in Five Couples Who Live Together Have Children from Multiple Partners

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More than 1 in 5 (21.2%) opposite-sex U.S. couples who lived together in 2021 had at least one partner who had children with multiple partners, according to a new U.S. Census Bureau report.

Having biological children with more than one partner, defined as multiple partner fertility (MPF), was common in many relationships, according to the Survey of Income and Program Participation (SIPP).

Married opposite-sex couples were less likely to include at least one partner who had children with other partners than unmarried opposite-sex couples (20.6% and 25.5%, respectively).

While the SIPP collects fertility information for all adults, the following analyses are limited to opposite-sex couples due to concerns related to the small number of same-sex couples in the sample.

As the first nationally representative survey to directly ask a question about that topic, the SIPP is a unique resource for understanding women’s and men’s MPF.

A new Multiple Partner Fertility Research Brief: 2021 provides an analysis of the MPF prevalence among adults generally as well as among coresidential couples, or couples who live together.

How Common Is Multiple Partner Fertility Among Opposite-Sex Couples?

Of the 69.1 million opposite-sex U.S. couples who lived together in 2021, 12.6 million (18.2%) had one partner with MPF and about 2.1 million (3.0%) had both partners with children from multiple partners.

Married and Unmarried Couples and Multiple Partner Fertility

Married opposite-sex couples were less likely than unmarried opposite-sex couples to include at least one partner who had children with other partners (20.6% and 25.5%, respectively).

Similarly, married opposite-sex couples were less likely than their unmarried peers to include only one person with children from other partners (17.7% and 22.4%, respectively).

The percentage of married (2.9%) and unmarried (3.1%) opposite-sex couples where both partners had MPF did not statistically differ.


The SIPP is a nationally representative, longitudinal survey administered by the Census Bureau that provides comprehensive information on the dynamics of income, employment, household composition and government program participation.

For technical documentation and more information about SIPP data quality, visit the SIPP Technical Documentation webpage. The estimates presented here are subject to sampling and nonsampling error.

Brittany King and Tayelor Valerio are survey statisticians in the Census Bureau’s Fertility and Family Statistics Branch.


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Page Last Revised - July 17, 2023
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