Bush Jr. was able to get into the Texas Air National Guard in 1968 because Houston businessman Sidney A. Adger, a good friend of his father's, asked the speaker of the Texas legislature to intervene on his behalf. His guard unit included other sons of the rich and powerful, such as Lloyd Bentsen III, John Connally III, John Tower's son, and Adger's own two sons (not to mention seven members of the Dallas Cowboys.)
The names of Adger, his sons, and their friends and business associates come up repeatedly in connection with two things -- Houston real estate development and the 1980's savings and loan scandals -- and are also mentioned more doubtfully in connection with the CIA and organized crime.
For example, one son, John Adger, was the partner of a Houston developer named Robert Corson, who was said to have been involved in money-laundering for the CIA and who got in trouble for savings-and-loan fraud. He was found dead in 1992 under suspicious circumstances.
James Bath was introduced into these same Houston business circles by a man named Sidney Trotter (who was the business partner of a fraternity brother of Adger's other son.) A resume of Bath's gives both Trotter and Sidney Adger as references.
Lan Bentsen, son of Senator Lloyd Bentsen, was another real estate developer who became implicated in the S&L scandals. He and Bath were involved together in business dealings with Sidney Trotter.
Most of what is written about Bath involves his Saudi connections, but these Houston business associations may just as significant. At the very least, it is clear that several figures involved with Bush or his National Guard unit went on to be involved in highly questionable activities.
On edit: I just found some more about Bath and Lan Bentsen in an article from 1991 at
http://www.krigskronikan.com/arkiv/bcci/Time%20Magazine%20-%20b28%20-%20A%20Mysterious%20Mover%20of%20Money%20and%20Planes--Bath%20-%20October%2028,%201991.html"Bath's penchant for secrecy has been frustrated by a feud with a former business partner, Bill White, who claims that Bath was a front man for CIA business operations. White contends that Bath has used his connections to the Bush family and Texas Senator Lloyd Bentsen to cloak the development of a lucrative array of offshore companies designed to move money and airplanes between the Middle East and Texas. White, an Annapolis graduate and former Navy fighter pilot, claims it was Bentsen's son Lan who suggested that White go into the real estate development business with Bath, a former Air Force fighter pilot.
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"Bath got his start in real estate in 1973 by forming a partnership with Lan Bentsen. One purpose, sources tell TIME, was to find investments for the Senator's blind trust. Bath and Bentsen have said they have not been partners for years, but secretaries at Bath's office still answer the phone with a cheery 'Bath Bentsen Interests.' Bath says he simply hasn't got around to changing the name of his company."