Research problem: This study investigates the difference in perceptions within the family-owned businesses of messages received from family members and outsiders to assess the role that relational familiarity (the amount of prior experience two people share communicating with each other) plays in internal business communication in these settings. Previous research has shown that this relational familiarity-along with experience with the communicative medium, the message topic, and the business context-lead to channel expansion (the ability to reduce uncertainty from a message with limited communicative cues) for business communicators. But the impact of relational familiarity on communication competence and personal biases between family members-which could impact the ability of relational familiarity to achieve its intended goals-has yet to be fully explored. Research questions: (1) Does increased relational familiarity between communicators lead to increased perceptions of message effectiveness and appropriateness in lean media settings? (2) In family business settings where familial biases may be prevalent, is increased relational familiarity linked to perceptions of increased sender likeability and lowered message negativity? Literature review: Channel Expansion Theory, which proposes that communicators can overcome the limitations of a medium by using their personal experience, guides this study. Previous research found that with personal experience with the communicator sending the message, a message receiver can enhance the limited capacity of a medium to convey cues that aid in understanding the message. Four perceptual variables-message effectiveness, message appropriateness, message negativity, sender likeability-result in benefits accrued from channel expansion and relational familiarity, such as reduced uncertainty and equivocality about the message topic. Methodology: A quasiexperimental setting was designed to elicit messages from business co-workers using email. Message senders were instructed to describe the same business problem in order for the recipient to understand the problem and decide how to proceed. Eighty-three family business owners, managers, and employees received one message from a family member belonging to the same business and one message assigned at random from a nonfamily member working elsewhere (a stranger). The 83 message receivers were asked to complete instruments measuring their perceptions of the messages. Results and conclusions: Results suggested that the relational familiarity between communicators played a significant role in improving message effectiveness and message appropriateness. Sender likeability was also enhanced when family members correctly identified the source of the message. The findings suggest that family members can benefit from channel expansion, though not as many members as expected, and that complex problem and task descriptions were communicated using lean media (communication channels that inhibit sending messages infused with communicative cues...