Sirius is more of a friend of Harry's. He was best friend to Harry's deceased father, James. James made Sirius Harrys' godfather.
Sirius Black
Sirius Black
Sirius Black, Remus Lupin, Peter Pettigrew
No. Sirius Black was one of James Potter's best friends. Upon discovering that Voldemort was hunting them, the Potters' went into hiding, naming Sirius as their Secret Keeper, meaning he was the only one to know where they were. At the last moment, Sirius switches from this role with Peter Pettigrew, whom he believed they could trust. Pettigrew betrays the Potters' to Voldemort which results in Voldemort's murdering them, and pins it on Sirius.
Because harry potters dad, James, had a friend called Sirius and Sirius was a werewolf and to keep Sirius company whilst he was a werewolf he learned to be an animagus.
Anthony
They're not actually related, as in "blood relatives", but Sirius Black is Harry's godfather.
Sirius Black was locked away in Azakaban prison.
Arthur isn't friends with sirius at the time because he does not yet know that Sirius is innocent.
Sirius is Harry's godfather.
Ron and Heirmionie
Harry Potter has 2 sons; James Sirius Potter and Albus Severus Potter