Donald Trump will be sworn in as U.S. president on Monday, ushering in another turbulent four-year term with promises to push the limits of executive power, deport millions of immigrants, secure retribution against his political enemies and transform the role of the U.

Eric Trump, 41, is the third child of Donald and the late Ivana Trump. Here's what to know about him as his dad returns to the White House.

"Trump is sui generis," one veteran Republican pollster told ABC News. "He is a unique figure in American politics."