His brother Jeb is married into one of the wealthiest Mexican families and hobnobs with the Mexican elite. There is much more, but if you understand Mexico and the Bushes blatant support of all things Mexico, then their tie to the Mexican leadership should answer more than does speculation about the Mexican secret service files on Bush. It is not illogical for one to speculate that the Bushes have direct relationships with that secret service. However, this is of no interest because they are wagging the dog with hillary (In this case, its wagging the hag who is a dog).
I have always thought of President G. W. Bush as an Eastern liberal elitist projecting a "Good Old Boy" persona - he may drive a pickup truck but his greatest legislative achievements after all have been in cooperation with Ted Kennedy.
You thesis makes more sense though. Temperamentally the Bush's are more like members of the Mexican power elite than their American counterparts.