Political figures have long used their families to route power and benefits for their own self-enrichment. In my new book, “Profiles in Corruption: Abuse of Power by America’s Progressive Elite,” one particular politician — Joe Biden — emerges as the king of the sweetheart deal, with no less than five family members benefiting from his largesse, favorable access and powerful position for commercial gain. In Biden’s case, these deals include foreign partners and, in some cases, even U.S. taxpayer dollars. The Biden family’s apparent self-enrichment involves no less than five family members: Joe’s son Hunter, son-in-law Howard, brothers James and...