Else Fred and George would’ve been a Slytherin, Hermione a Ravenclaw, Luna a Hufflepuff and Cedric a Gryffindor. You can fight me on this.
This is why you can have an entire family of Weasley’s all in Gryffindor, or an entire family of Malfoy’s all in Slytherin – because they were raised to value honour and bravery/ambition and loyalty respectively.
(( OOC: One more time for the people on the back. ))