You were Sirius's son and you were in Azkaban for 6 years, you were 10 years old when you were sent in Azkaban because you were crazy young. When you were freed from Azkaban, you made new friends, Harry, Hermione and Ron. And Harry didn't see your father since 1 year, so you all finally will get in Grimmauld place where your father is, Remus Iupin, the Weasleys and Harry, Ron and Hermione were with you.

When you enter, Harry rushed in Sirius' arms after the Weasleys greeted you and hugged you because they finally see you again, your father didn't even notice you but Remus did, he knew you since you were a baby because you're his bestfriend's son.

So he hugged you and asked question etc until you looked at Sirius, your father, seeing him pulling away from Harry and Harry point you and Sirius froze and his eyes widen, seeing his son again after 6 years did something to him.. and he was shocked but excited and happy, you looked like him, dark curly hair, his eyes..