I believe it's the fact that we live in Britain that makes it a very non traditional name. Britain has never been big into accepting other, and purebloods even less.
I understand well, and that's why I haven't invited anyone at the manor. However in your nephew's case, invitations were sent out. In fact one was received in this very house, and I believe I was invited by proxy. I might have a newborn, but I have not forgotten my manners. It's a faux pas I would expect from your sister, not Theo, and yet it has happened. C'est la vie.