Political dynasties exist in practically every variant of democracy. Yet, the literature has not theorized about how particular forms and functions of political dynasties benefit their members. We argue that horizontal dynasties—multiple members from a family holding political office concurrently—leads to higher levels of local government spending. Horizontal dynasties increase local government spending by replacing potential political opponents who may oppose spending with members of the family. Members from the same family have aligned preferences, and these preferences reduce conflict and increase coordination across offices, allowing politicians to pursue their political goals. We test this argument’s implications in the Philippine context. Employing a regression discontinuity design on a sample of mayors, we show that (i) horizontally dynastic mayors have higher levels of local government spending and (ii) increasing local government spending is driven by preference alignment, which leads to less conflict and greater coordination between politicians.