There is a big difference between leveraging your fame to make money when you leave the presidency, and selling access to the presidency during your term in office. Family members profiting from their connection to the president is a problematic area that merits oversight, but is qualitatively different.
Being the family member of a senior government official as well as a famous individual means that there are two separate ways you could, theoretically, be able to profit. I have seen no evidence that Bill Clinton's speaker's fees from people he had known for a long time was related to the fact that he was Hillary Clinton's husband. Certainly, I have seen no credible evidence that the Obama administration made decisions influenced by his speaking engagements.
I do not think people writing books while holding official positions, or being family members of those in official positions, can easily be painted as a corrupt practice.