Harry Potter raised by Sirius
Sirius arrives First After James and Lily were killed, He is going to go after Peter, but then he remembers the promise he made James and Lily that if anything happened he would look after Harry.
So Sirius Takes Baby Harry To Potter Manor.
When Hagrid arrives and can't find baby Harry he contacts Dumbledore.
Dumbledore rushes to godrics Hollow he uses multiple different spells to try and find any clue of where baby Harry is.
Harry is then declared Alive but Missing.
People try to find baby Harry but nothing works,all they know is that he is alive wherever he is.
Years go by and with Harry being raised By Sirius he Knows all about magic,the wizarding World, His parents, The War Etc.
Sirius having been friends/family with lily Knows how to actually fit in with muggles So he and Harry go into the muggle world Using glamours To not be recognised.
Harry loves the differences In the magical world and the muggle world, Especially when he reads "Expert Books on muggles" and has the best time laughing knowing that the authors were idiots and clueless wizards and witches will be acting so strange in the muggle world.
Harry grows up to be a Handsome young man,Who is cheeky and kind, He is a bookworm using all the books in Potter Manor to learn all sorts of magic.
He starts flying as soon as he is able.
He inherited his Dad's love for pranking and With his mom's smarts he is able to use normal spells,potion in creative ways to prank Sirius.
Harry knows all about the maurders And how Snape was obsessed with his Mom, willing for himself and his dad to be killed so he joined Voldemort so he could have her for himself. (James,Sirius,Remus didn't bully Snape for no reason they only retaliated)
Harry grows up with house elves as his friends, He treats them like actual people (not like Malfoy) And he is even able to use puppy dog eyes on them to get their help with pranking Sirius.
More years pass, and when Harry arrives at Hogwarts all hell breaks loose as People where losing hope that he was actually alive. (You can choose if Harry has known Hermione for years Or if he meets her when he joins Hogwarts.)