Objective
This study examined how the timing and structure of parents' relationships are related to father engagement and cooperative coparenting in the United States.

Background
Responses to nonmarital pregnancies have shifted; mid-pregnancy (“shotgun”) marriages have declined while mid-pregnancy cohabitations have significantly increased. These less institutionalized family forms may create ambiguity about fathers' roles as parents and partners.

Method
Drawing on data from the Fragile Families and Child Well-Being Study, a longitudinal birth cohort study (n = 2,752), we estimated conditional associations between a five-category measure of parents' relationship structure and timing at the focal child's birth—(a) mid-pregnancy cohabitation, (b) mid-pregnancy marriage, (c) pre-pregnancy cohabitation, (d) pre-pregnancy marriage, and (e) nonresident couples—with measures of father engagement and cooperative coparenting when the child was 1 year old. Supplemental analyses evaluated these outcomes at Ages 3 and 5.

Results
At Age 1, fathers in mid-pregnancy cohabitations reported less cooperative coparenting with the child's mother compared to fathers in pre-pregnancy cohabitations. In contrast, fathers in mid-pregnancy marriages were more engaged with their children than fathers in pre-pregnancy marriages.

Conclusion
Fathers were particularly engaged with young children following mid-pregnancy relationship transitions but were less cooperative coparents with the child's mother. This study joins research suggesting that fathers with low socioeconomic status may be embracing a new “package deal” in which the father–child relationship is central, and the father–mother relationship is secondary.