• fertility;
  • fragile families;
  • kin networks;
  • social networks;
  • social support;
  • stepfamilies

Recent research has documented the high prevalence of having children with more than 1 partner, termed multipartnered fertility. Because childbearing is an important mechanism for building kin networks, we theorize that multipartnered fertility will influence the availability of social support for mothers. Analyzing 3 waves of data from the Fragile Families study (N = 12,259), we find that multipartnered fertility is negatively associated with the availability of financial, housing, and child-care support. Our longitudinal evidence suggests a bidirectional relationship in which multipartnered fertility reduces the availability of support, and the availability of support inhibits multipartnered fertility. We conclude that smaller and denser kin networks seem to be superior to broader, but weaker kin ties in terms of perceived instrumental support.