While the siblings I have interviewed are less infamous than the Boothe brothers, I, too, have found that family stories vary among siblings. The most common difference that I have found is in the perception each sibling has of the parents, especially in families in which the siblings are separated by a wide age gap. A first born raised by very young parents on a budget will have a very different view of, and stories about, his parents than will the youngest son who was born when the parents were 40 and wealthier. One might have spent his first ten years in a cramped urban apartment while the other lived in a big house in the suburbs. One might have viewed his parents as carefree and happy; the other, as anxious and somber. Age difference between siblings is a big factor, but there are many others--temperament, gender, intellect, personality, talents, and so on. Many times, I have heard siblings describe their parents so differently that it is hard to believe they are talking about the same people!
Be cognizant of these differences when collecting your family stories. Do you wish to preserve only one point of view in your stories, or do you want to include a more well-rounded perspective?
I learned this lesson the hard way once, by attempting to film an interview of two sisters. Not only were they a decade apart in age, they had very strong (and very opposite) perspectives on almost every family member and event. They spent the whole interview bickering on every detail. Be careful of the sibling dynamic when collecting your stories!