Siblings

My Psychology lecturer would be over the moon at my reflection on the study of habits being pre ordained by DNA “nature” or by the “nurture” of the environment and parents.

What makes one sibling the “black sheep” of the family starting night clubs at the age of 12, smoking, drinking and making it a mission to disobey parents? This VS the one motivated to carve out a life with finances and position etc.

It’s a question that’s baffled me for a very long time and I don’t see an answer to it in-sight in the near future.

If anyone can enlighten me, I’m open to suggestions.