Maybe his dad was also named Samuel, so little Samuel was called by his middle name - a very common thing to do. No big deal. Barack “Barry” Hussein Obama should know that. Of course, Barry wouldn’t choose to go by HIS middle name, at least not in public.
That’s exactly the way it happened with my husband’s name. His mom didn’t want anyone calling his dad and him “big” and “little” so his family uses his middle name.