What was the role of the family in individual reproductive decisions during state socialism? Can the family help to understand regional variations in fertility decline? This study provides an in-depth analysis of family relationships and their influences on individual reproductive decisions during the transition from first to second birth in Soviet Ukraine. Life history interviews are used to compare the western and eastern borderland cities of Lviv and Kharkiv, respectively, around 1950-1975. The findings reveal that regional differences in intergenerational ties and spousal cooperation shaped two reproductive strategies of transition to second birth, specifically postponing in Kharkiv and spacing in Lviv.