Identities are comprised of sets of meanings that people apply to themselves. These meanings vary in both content and quality, with important implications for individuals' actions, emotions, and commitment to their identities. In this research, we reveal how men's significant others serve as important sources of identity meanings and are key to how men interpret and enact their identities as fathers. Using data from in-depth interviews with low-income fathers, we demonstrate that fathers whose significant others offer positive examples of parenting, articulate concrete expectations, and provide explicit evaluations of men's performances, have more nuanced ideas of who they want to be as fathers and can more effectively translate those ideas into clear lines of action and engaged parenting behavior.