Approximately one-third of all infants are born to parents who are not married. Families in which the parents are cohabitating or living separately are considered to be fragile and at risk of dissolution and poverty. This report highlights findings from the Fragile Families and Child Wellbeing Study and the Time, Love, Cash, Caring, and Children Study regarding the relationships between unmarried parents. The results can be used to assess need and target services to support these families. The Fragile Families and Child Wellbeing Study is following a cohort of 3,712 children born to unmarried parents and a comparison group of 1,186 children born to married parents during the same time period. At the time of the child's birth, 51 percent of unmarried parents were cohabitating and 31 percent were dating. Almost half of the unmarried mothers had an income of less than 200 percent of the poverty level and one-third of unmarried men were defined as poor. Only 20 percent of married parents had an income below the poverty line. Unmarried parents also were more likely than married parents to report having children with different partners, substance abuse, partner violence, and low educational achievement. Although most of the unmarried couples believed that they would eventually marry their child's parent, one-third of dating parents had separated within one year of the child's birth. Marriages were more common among cohabitating couples, employed parents, and women with higher educational achievement. Seventy-five of the participants in the Fragile Families Study were interviewed for the Time, Love, Cash, Caring, and Children Study to explore factors that influence their relationships. The couples identified financial as well as relational barriers to marriage. They perceived marriage as an ultimate goal after achieving economic and emotional security. The longitudinal studies will continue to collect information about racial and ethnic differences, child wellbeing, and necessary services. 17 notes, 2 figures.