Elon Musk is known for bemoaning the declining birthrate.  He's doing his part to remedy that situation, having fathered eleven children himself. But, as usual, he's not fitting in with the other billionaires who are very interested in ways to reduce birthrates.

The other billionaires aren't so keen on babymaking.

Most of the billionaire class seems convinced with a religious fervor that overpopulation is responsible for the world's ills, especially climate change.  Britain's Prince Philip is famous for saying, in 2009, that when he died, he wanted to come back reincarnated as a virus, to solve the overpopulation problem.  King Charles has spoken out about problems related to overpopulation since the 1970s.  Prince William recently gave a speech about Africa, particularly, having an unsustainable birth rate/ 

The British royal family is not alone.  In Bill Gates' Innovating to Zero TED Talk in 2010, he expressed hope in reducing population by "10 to 15%" to meet climate goals.  

The Rockefellers, in particular, have been involved in population control schemes since the 1950s.  Assisted by hefty donations from groups like the Ford Foundation, they have been funding various projects to restrict the births of low-income people around the world.