Using data from the Fragile Families and Child Well being Study (N= 2,656), we examined the association between intergenerational relationships and parents' union stability five years after a baby's birth. Results showed that more amiable relationships between parents and each partner's parents, and more time children spent with paternal grandparents, were associated with increased odds that parents were co-residing by the time their focal child was age five. More time that children spent with maternal grandparents reduced union stability, although this result was not robust to methods that better address selection. These findings underscore the importance of the broader social contexts affecting couple stability. Findings further suggest that even amidst changing demographic conditions, intergenerational family ties are important for couples-and by extension-their children.