Adopted and second children still represent different environments. If the adopted child wasn't adopted at birth, their formative years would greatly impact what is perceived as nature. Its a meme that parents are generally more cavalier and relaxed with later children than they are with the first, and that is a significant environmental variable.
Nature definitely hardwires in some baseline chemistry, but those first couple of years have a huge impact on how a child will deal with that chemistry.
Yes nurture has an effect, but the current science suggests that our DNA has an even greater determination of who we are than we ever imagined, the degree of which is incredibly surprising and non-intuitive. It would suggest that we become who we are determined to be, no matter the early childhood variables.
Nature definitely hardwires in some baseline chemistry, but those first couple of years have a huge impact on how a child will deal with that chemistry.