Enlarge / White House advisor Stephen Miller in 2017. (credit: Drew Angerer/Getty Images) White House advisor Stephen Miller is widely seen as the mastermind behind President Donald Trump's controversial policy of separating parents from their children at the US southern border. Yesterday, Splinter, a news and opinion site that was previously known as Fusion, published Miller's personal cell phone number. When Splinter and others started tweeting out Miller's number, it got the attention of Twitter's content police.