sound and picture on 2 TV's not synced.

I have 2 TV's...one in kitchen and one in living room. When they are both on the same channel, one lags behind. Because they are close to one another, you can hear the sound and it is distracting for both viewers.  I have been told that adding an HD box to the one in the kitchen will not fix the problem.  Is this true and if so, is there a way to get them synced up