Sirius was a handsome man with dark black hair and brown eyes, he was short and "not the thinnest".
Sirius always were a jolly man that could not have been taken serious by his elders, siblings, wife or children. Although the eldest of Phineas' children, he lacked sense of responsibility and wisdom.
Born as the eldest child of Headmaster Phineas Nigellus Black and School Matron Ursula Flint, Sirius, his sister and brothers grew up in Hogsmeade and all attended Hogwarts. Sirius attended from 1888 to 1895 and was sorted into Slytherin House.
Around 1931, Sirius inherited 12 Grimmauld Place from his aunt Elladora Black. He shared this home with his son Arcturus, daughter Lycoris and grandchildren Lucretia Black and Orion Black. Although kind to the House-Elf Kreacher, every member of the family considered him in a "permanent bad mood" and considered Arcturus as the real master of the House.