There are different reasons kids are singled out from the rest of their family as being the black sheep. One way they can be black sheep is by having different a instinct stack than the rest of their family.
Your instinct stack is the prioritization of instinctual responses you have to social situations. Self-preservation kids appear low-energy, like they're trying to preserve their energy. Social kids obviously have an easy time in social situations and diffuse intensity, while sexual kids emit intensity (nothing to do with sex in this context- that's just the name of the instinct. Sex comes into play later when they become adults. At this age, the kids are just experiencing a need to show a lot of exuberation or other intense feeling).
The word "stack" just means that while each of us has all three of the instincts, we have them stacked on top of one another in order of preference. The first two, we can access fairly well, while the third, way at the bottom, we tend to leave underdevelopped.
In these cases, the black sheep of the family would be the kids whose energy doesn't fit into the tempo and intensity level of the rest of their families. Black sheep kids can be found in every combination of instinct stack-dominant family, but I have a special heart for sexual kids who are born into self-preservation families, because that's the biggest gap in energy levels. Self-preservation parents with sexual kids are often just beside themselves trying to understand their alien kid. Those kids are told that their intensity is too much, too loud, and embarassing.
I was raised in a self-pres/social dominant family, so there was pressure to keep the intensity low, laid-back and the tempo diffused, although we did break into crazy-intense debates or dance-offs every once in a while.
As adults, the black sheep has to consciously figure out their true expression for themselves, and learn how to be comfortable with how they express their own emotions.
The other day I bought an ipad with some birthday money and I was so excited, I took a picture of myself. It turned out like this.
I looked at the picture I just took, and I was like WTF, that's not how I feel, so I took another picture.
That's how I really felt.