Describe the Buchanans and their background. How are they related to the narrator in The Great Gatsby?

Tom and Daisy Buchanan live in East Egg, the fashionable and extravagant neighborhood of "old money" on Long Island.  Both grew up in Louisville among the elite of society there.  Daisy is the cousin of Nick, the narrator of the story; and Tom is a former classmate of Nick's when they both attended Yale.  Daisy, we learn mid-way through the novel, married Tom only after Jay Gatsby left for the war, but she was and is still in love with Gatsby.  Unlike her husband Tom, Daisy has always been faithful in their marriage.  Fitzgerald also hints that Tom may be physically abusive to Daisy.  Gatsby lives directly across the bay from the Buchanans in an elaborate house he purchased only in hopes of being able to see Daisy again.  He stages outrageous parties in the hopes that she might one night wander in.  This extravagance is in direct contrast to Tom's neglect.  Both Tom and Daisy represent the "old guard," those whose families have a history of wealth, while Gatsby represents those who made their fortunes in the booming economy preceding the Great Depression.