Even if you do discover that you are not the first to chronicle the story of your clan, check the details that have been uncovered already; it can't hurt to ensure that the details are actually correct.
This process is key to establishing later lines of research, so try to get as much information as possible, bearing in mind that some of what you hear may not be strictly accurate - memories can fade over time, whilst many of our relatives are referred to by 'pet' names that are not the same as the ones they were born with. You will almost certainly hear stories that may have been passed through the family for generations, and it will be your task to check their veracity as well. Take some time to see if anyone has already done some family history. Even if you do discover that you are not the first to chronicle the story of your clan, check the details that have been uncovered already; it can't hurt to ensure that the details are actually correct.