Are you crazy?
I know people like to roll their eyes when conservatives talk about the sanctity of marriage, but are you really trying to say that there is a stronger bond between Obama and Cheney than there is between Bill and HIllary Clinton?
And ins't this idea of a lineal dynasty based on patriarchal constructs that should be rejected? If the Clintons had a son, even one younger and less accomplished than Chelseas, wouldn't he be the "heir" under your old stilted definition?
If the monarchy of Great Britain passed from Elizabeth to Prince Phillip rather than Prince Charles would that make it a model of egalitarianism and democracy?
If a presidential couple had adopted a child, would that child qualify?
If George W. Bush appointed Laura's nephew to a Cabinet post, I'm quite sure there would be charges of nepotism, in spite of the appointee not being related to W.
Having the presidency bounce back and forth between two families for almost a quarter century isn't consistent with what we say about our country. I don't care if the family links are identical twins or a one-night stand hook-up. I've got to believe we can find someone qualified to be president who is not a member of these two families.