It was said in defense of the existence of the Nehru-Gandhi ruling dynasty of the Congress Party in India that political dynasties were common throughout South Asia. This is certainly true in India where politics in the Indian states are usually a family affair with the party founder usually passing on control either to a son or daughter or, if a suitable heir is not available in his immediate family, to a nephew or niece.
While there are many political dynasties in America with most states possessing at least one, the most successful at the national level has been the Bush family of Connecticut, which has had three generations of politicians in Washington at the senior level starting with Senator Prescott Bush and ending with President George W. Bush, whose younger brother Jeb was also governor of Florida. The Kennedys of Boston, Massachusetts have had three generations but there was a major upgrade from the first to second generation and then a major downgrade to the third generation. Joseph Kennedy was ambassador to London in the late 1930s but ended his political career early when he fell afoul of President Roosevelt and was judged to be a Nazi sympathizer. But three of Joe's sons did quite well: John F. was president from 1961 to 1963, when he was assassinated in Dallas; Robert F. was attorney general under his brother, senator from New York and then the leading contender for the Democratic nomination before he was in turn murdered in June 1968; and Edward M. was one of the longest serving senators in the Senate from 1962 until his death. But the next generation has produced a representative, Patrick, and nothing higher.