Sports fans often swap odd familial statistics: three brothers playing in the same Australian cricket team, a father and son as rival managers in an FA Cup game. Because theatre is prone to dynasties, DNA links are common in casting – there have been several productions of Chekhov’s Three Sisters in which the actresses were actually siblings – but it surely must be unusual for dramatists who are brother and sister simultaneously to have plays running in London.Having staged a revival of her own medical drama Tiger Country at the Hampstead Theatre, writer-director Nina Raine has dropped the pre-hyphen side of her job title and applied the post-hyphen side to transferring her brother Moses Raine’s play Donkey Heart from the Old Red Lion Theatre, where it had a celebr