This data is pretty interesting. Of course, it's hard to separate out or even infer the causes as nature vs. nurture (which the article is careful about) but the part about twins was the most striking for me:

"Twins' tendency to choose the same occupation, at 24.7%, is even more striking."

A possible explanation was provided above:

"Whether identical or fraternal 2, twins are also more likely to be raised in a similar environment — parenting styles may differ as a parents add more children to their brood, but twins will likely be exposed to a similar parenting style."

Also, being raised in the same time period would also expose you to the same cultural/economic/societal factors - all of which can change with time, and also may affect your choice of career. (i.e. the proportion of math_CS parents could be different from the proportion of math_CS children just because of the different time periods in which each grew up)