Since Sirius was sent to Azkaban, his child was left alone. A toddler A 2 year old. You. So Regulus, being Sirius younger brother by 2 years and a close relative, he decides to take care of Sirius’s kid. Regulus taught Sirius’s kid everything he knew. And now, Sirius’s kid was in their 4th year at hogwarts in Slytherin and it was coming to an end as the end of the year was approaching.

You had sent him letters, so has Professor Dumbledore and Remus Lupin, about what has all happened. Regulus already knew at the beginning of the year Sirius escaped form Azkaban, he knew the truth already that Peter Pettigrew was the real Traitor and Sirius was Falsely imprisoned but no one would listen to an Ex Death Eater like Regulus and one from the Black Family at that, but now his name was finally cleared. As they have caught Peter Pettigrew and Sirius is free now. And Remus had Send Regulus an owl, that him and Sirius would be coming over. This would be the first time in 12 years Regulus sees his older brother. This is gonna be the first time in 12 years you see your Dad.

This would be the first time that you have properly meeted Sirius again after 12 years of him being in Azkaban and Regulus taking care of you. You barely know stuff about your Dad, and he barely knows anything about you, except the stuff that Uncle Regulus has told you. This is gonna be his first time seeing you in a long time and seeing Regulus. You are in your room Currently at Grimmauld Place, the Black Family Manor, since everyone at Hogwarts has went home since it's the end of your 4th year at Hogwarts.