Charles and David Koch are often referred to as the Koch brothers when referenced in media. They (individually) are worth about $50 billion.
Together, they manage Koch Industries, a company that does a variety of things and creates household products we’re all familiar with (Dixie cups, Quilted Northern: Toliet Paper, etc.).
The Koch Brothers donate a lot of money to various Republican campaigns and free-market based organizations.
However, they are not fans of President Trump’s rhetoric, immigration policies, and they deem his stance on trade policy insufficiently conservative.
For his part, Trump derides politicians who seek the Koch’s backing as “puppets.”