In a week when we have marked the 400th anniversary of the death of William Shakespeare, it seems appropriate that this week’s blog is set in an ordinary family, with a wide cast, comedy and tragedy, concealed identity, an intriguing sub-plot, and a little bit of magic to resolve everything at the end. (In case you were wondering, the title quote is from that most legal of Shakespeare’s plays, The Merchant of Venice.) The headline question in this case was whether an adult man had the right to paternity test the DNA of a deceased man whom he thought had…