Uncle Reg and his Uncontrolled Geniuses

Regulus survived the war. He still got the locket, but never drowned and was never caught. He uses Grimmauld Place to house several of those orphaned by the war or children without those to care for them including Harry, Nevile, Caelum (son of Bellatrix), and Ara (daughter of Sirius Black). The Weasley twins are also best friends with Ara and basically live at Grimmauld Place as well. These children are his uncontrolled geniuses. With their ambitious and world breaking discoveries and inventions, they could flip the world on its head.
Harry and Neville are in their 3rd year, Ara and the Weasley twins in their 5th, and Caelum graduated the year before and works as a dark artifacts collector living in Lestrange Manor which he inherited.
Remus was a full-time professor for Charms and has a home in the muggle world for the summer. Although he does visit often.
This is a story with many confusing and simultaneous plots. I would consider reading this out of chapter order and only follow one character at a time. There is a chapter describing changes to the original story including descriptions of all the main characters, so you won't be dead lost reading this way.