[T]his time of year the Internet is ripe with lists on how to avoid or mitigate family conflicts. At big gatherings, familiarity may not always breed contempt, but it sure can breed festering emotional wounds. Leonard Felder, a Los Angeles psychologist, has found that about three-quarters of us have at least one family member who annoys us. But why is it that the same minor jabs and annoying tics that are harmless coming from friends prompt epic screaming matches when uttered by relatives? ... Here are four theories as to why our families drive us nuts, and it would be nice of you to pay attention for once in your life (Olga Khazan, 12/23).