His girlfriend, Emma Webster, 16, gave birth to Ben on Tuesday after 14 hours of labour. Sean went to the hospital where he mopped Emma's brow and rubbed her back.
"When I first saw Emma afterwards she was holding the baby. It looked just like a mushroom. I looked at Emma and smiled but I felt very embarrassed and nervous," he told the News of the World.
"I hope to stay close friends with Emma as long as possible ... I'm very happy with Ben but if Man United win the league it will have been a perfect year."