Lack of communication in families is primarily caused by a member or members of a family not thinking of the other members' needs--either emotionally or physically, or a mixture of the two.
This lack of communication can occur when any member of a family is preoccupied with other factors, such as work or a hobby. This individual does not make the other family members feel important. In turn, this causes a failure to communicate with the family member who is preoccupied. At this point, family members may begin to feel that their feelings will not be validated, as they are obviously not important to the other person.
Often, misunderstanding is one of the root causes--if not the primary cause--of poor communication. A family member could very possibly be annoyed or upset about his or her day at work, but that person's silence or bad temper can be misinterpreted by other family members as anger which is directed towards them. Family members may express their hurt at being ignored or treated poorly by responding with a bad temper towards the "offending" family member--thereby causing unnecessary discord within the family's dynamics.
Another cause of poor communication is when one person will focus on the other person and blame him or her, rather than focusing on the problem or issue at hand. This individual will not express his or her dissatisfaction on an issue by stating, "I feel..."--but rather, he or she will begin statements with the phrase, "You make me feel..." This causes the other person to feel attacked and defensive, and therefore less likely to attempt to fix or resolve the issue--creating unnecessary bitterness about the relationship.