You’ll stay with me? Until the very end, said James. They won’t be able to see you? asked Harry. We are part of you, said Sirius. Invisible to anyone else

You’ll stay with me? Until the very end, said James. They won’t be able to see you? asked Harry. We are part of you, said Sirius. Invisible to anyone else (J.K. Rowling, Harry Potter and the Deathly Hallows)