WASHINGTON - Growing up without a father left a painful hole in his heart, President Obama told a gathering of boys at the White House yesterday in a remarkably personal Father's Day weekend message. He implored fathers everywhere - and the youngsters when they are a bit older - to stay home and stay involved in the lives of their own children.

"This isn't an obligation," said the father of two in a message to millions of wayward dads. "This is a privilege to be a father."

Obama spent hours yesterday with teenagers, young men, community mentors, and everyday dads in hopes of launching what he called a national conversation on responsible fatherhood. Each story was personal. But one of them commanded the most attention: his.

He spoke at length about how his father, Barack Obama Sr., left home early. The future president was just 2 at the time and saw his father only once more, at age 10, a short visit that still left a lasting imprint.

"I had a heroic mom and wonderful grandparents who helped raise me and my sister, and it's because of them that I'm able to stand here today," he told a throng of youngsters. "But despite all their extraordinary love and attention, that doesn't mean that I didn't feel my father's absence. That's something that leaves a hole in a child's heart that a government can't fill."

The White House is sponsoring forums around the country this summer and fall to promote programs for mentors and fathers and to see how the federal government can support them.

And then there is Obama's personal attention. Only issues of special importance to a president get a full afternoon of his time.

Obama mingled with the youngsters on the South Lawn as they chatted with other big names from entertainment and sports, ate barbecue, and got some lessons about life.

Danilo Downing, a 16-year-old who just finished his sophomore year at Yorktown High School in Arlington, Va., said the White House visit changed his life. He has never met his father, and connected with the president's comments.

"I think of him as my father now," Downing said after he shook Obama's hand and got a pat on the back. "He's really special to me. He's an amazing man."