As Professor Trelawney tells us in Book 6, whenever 13 people gather, the first to leave the group will be the first to die. In chapter 5, 13 of the survivors of Voldemort’s attack (Harry, Ron, Hermione, Mr. and Mrs. Weasley, Fred, George, Bill, Fleur, Ginny, Hagrid, Tonks, and Lupin) all drink firewhiskey together. Lupin is both the first to finish his glass (he had “drained his glass in one”) and the first to leave the gathering

This also happens in the fifth book, where 13 people gather at Grimmauld Place and Sirius is the first to rise from the table

Ooo