Dear Sirius
I know that your mother has already written to you, but I feel that it is my duty, as a father, to write also.
You have greatly upset your mother by your being placed in Gryffindor and seeming not to care about this terrible misfortune. I demand that you write a letter of apology to your mother this instant. You are a born troublemaker, Sirius Orion Black, but nevertheless you will not disgrace my family!
Your father, Orion Black.