The 19-year-old model became an overnight sensation when the issue hit newsstands last week.
"She's a great gal," the New York Daily News quoted Fred Upton as telling Fox News.
"I got a lot of my colleagues that are asking if I was adopted," he added. "It's been fun to watch her grow up. ... She's only 19, but we're all proud of Kate."
The Republican legislator chairs the House Committee on Energy and Commerce.