Yes, it's possible that there are strong genetic predictors of household income, as a lot of people seem to want there to be for some reason, but when predicting the behavior of a child, their immediate circumstances are a much more parsimonious explanation for their behavior than some genetic factor strongly predicting both the circumstances and the behavior. I'm not saying that genetics being somewhat causally upstream of income is an inherently bad hypothesis, but this kind of correlation analysis doesn't support it as well as it does an environmental influence on time preference