I have a somewhat challenging family, but we seem to always manage to work it out. I have theories on why we are able to get past these things.
I think misunderstandings and fights often occur because we (the "royal we," lol) don't communicate well, and people don't say what they really mean, and they don't think about how their words are being interpreted by others -- in effect, we often "talk past" one another.... and so resentments and hurt feelings are not resolved, and continue to fester.
I also believe that we have to accept one another's faults a bit more. Perhaps this one is flaky or that one is sarcastic, but just bearing that in mind when you are talking to that person and thinking "I'm sure she didn't mean it that way, she can just be so sarcastic." Or even saying TO HER: "Wow, do you really mean that, or are you just being sarcastic?"
I find so many of the fights and problems begin when assumptions are made and words and actions are assigned meaning by the receiver that were not intended by the sender. For example, I have said things like this many times, "Well, I can see WHY she reacted that way -- it is in her personality to take those types of comments to heart, not as suggestions but as criticism. You should tell her you didn't mean it that way."
I guess I am blessed with a family that, although not perfect, is at least willing to listen to one another and are humble enough to apologize to one another.
I also remember my parents telling us from early on: Be good to your brothers and sisters; protect one another, stand up for one another. When Mom and Dad are gone, they are your family of origin and it's very comforting to be with them as an adult, they will be the only people who have known you and loved you YOUR WHOLE LIFE.
I guess I should be very grateful. :)