This descriptive study of millions of US Facebook users documents "friending" and communication patterns, exploring parent-child relationships across a variety of life stages and gender combinations. Using statistical techniques on 400,000 posts and comments, we identify differences in how parents talk to their children (giving advice, affection, and reminders to call) compared to their other friends, and how they address their adult sons and daughters (talking about grandchildren and health concerns, and linguistically treating them like peers) compared to their teenage children. Parents and children have 20-30 mutual friends on the site, 19% of whom are relatives. Unlike previous findings on family communication, interaction frequency on Facebook does not decrease with geographic distance.