J.K Rowling told us that Fred [ one the Weasley twins] was born before George. If you think carefully about it, F comes before G and in the books they refer to them are Fred and George not George and Fred. Quite often Fred talks before or takes lead before George.
-Bit more on the twins. In Harry Potter and the Deathly hallows [part 2] Fred very sadly dies, He died in a explosion probaly caused by Rookwood.
In Harry Potter and the Half blood prince, Fred and George set up a joke shop; with the money that Harry gave them after he won it in the triwizard tournament.
They sold some amazing products such as : Puking pastiles, to get you out of class; Extendable ears, to listen in on conversations; love potions; pugmy puffs; and lots of other fun products.
Fred and George are the Jokers in the book series, and sre very sucessful with their joke shop.