Young but a Weasley

The day's Ginny's birthday. Day 11th August 1981. Voldemort never existed but the world was plagued by Grindelwald, whom Dumbledore's subdued for the last 35 years.
What happens when a helpless, desperate woman leaves her only son for the Weasleys to take care of whilst providing enough of wealth for them to use before she dies untimely.

Well, essential shitload of a fuckton of chaos. And also, a little spoiler, he gains magical powers after 15-17 years of life.