I think it's:
The weasley kids from the Harry Potter Books.
Our first has his hands on the money;
Bill the eldest, works for the wizard bank Gringotts as a treasure hunter.
Our second has his hands in fire;
Charlie the 2nd, works with dragons.
Our third was an outcast for years.
Percy is a prick and was kind of alienated from the rest of the family until the very end of the series.
Our fourth and fifth were together:
One dead, one deaf, or nearly so.
The twins, Fred and George, one got his ear chopped off, the other killed.
Our sixth was tall and most important,
Ron, one of the main characters, also supposed to be tall.
Our seventh was different from all the rest.
Ginny, the only girl.
Friendly and welcoming, who are we?
The Weasley kids.