(Reuters) - Barack Obama, whose Kenyan father left his family when the future U.S. president was 2 years old, said Saturday he still thinks about how things would have worked out had his dad been there. "I felt his absence. And I wonder what my life would have been like had he been a greater presence," Obama said in his weekly radio and Internet address a day before Father's Day in the United States. The president said that being a father was "sometimes my hardest, but always my most rewarding job," and called on other fathers to make spending time...