The "Koch brothers" are Charles and David Koch, who own the multinational company Koch Industries. Their combined personal net worth may be as great as $100 billion. They have been hysterically anti-Trump to the point of even supporting delusional efforts at the Republican National Convention in July 2016 to somehow deny the nomination to Trump. The Koch brothers are not pro-life, and tend to undermine efforts to strengthen American sovereignty and border security.
The Koch brothers fund the LIBRE initiative, which pushes for amnesty for the more than 11 million illegal aliens in the United States.
Despite their wealth and repeated attempts to gain political influence, it is difficult to point to anything the Koch brothers have achieved that is positive in politics. Sometimes they secretly fund harmful causes while concealing their role.
There are additional Koch brothers who do not participate in the political projects of Charles and David.