Sirius escapes Azkaban
A few Years after Sirius was Captured And sent to Azkaban, he keeps having nightmares of Harry being abused or killed.
So he comes up with a plan, He escapes Azkaban, And Then Finds where Harry is living, and then using Magic Makes A muggle Rent him a House across the street from The Dursleys. He then uses the Fidelius Charm to Hide the House And uses himself as the secret keeper.
Sirius Claims his Lordship, And removes Everyone From The family.
He Makes sure Kreacher can't Betray him.
He then Kidnapped Harry After seeing how Harry was being abused.
Dumbledore has no idea Harry isn't living with the Dursleys Anymore.
Sirius raises Harry To the best of his ability, Teaching him all about magic and his parents.
Harry even Helps with Kreacher treating him kindly and like a family member.
Kreacher still doesn't like Sirius, but beacuse he loves Harry He becomes civil to Sirius. He will never betray Sirius as that would mean betraying Harry.