Fred and George Weasley (born April 1, 1978) are fictional characters in the Harry Potter series of novels, created by J. K. Rowling. They are the twin sons of Arthur and Molly Weasley and the younger brothers of Bill, Charlie and Percy. They are older brothers of Ron and Ginny, who are both members of Harry Potter's close group of friends. The twins revel in practical jokes and tricks, and are generally considered extremely amusing by both other characters and readers of the books.
While their best friend is Lee Jordan - their classmate, dormmate and fellow prankster - the twins are also good friends with Harry, having played Quidditch with him for Gryffindor. In fact, they generally treat Harry better than they treat Ron (no doubt due to Harry's own inner rebel spirit); they love to torment Ron and Percy, but they appear to be close with Ginny (who closely resembles them both in appearance and personality) and vice versa. As the rest of the Weasleys, they have flaming red hair and are described as being on the shorter, stockier side like their 2nd older brother Charlie. They are generally considered to be very funny, and seem to be quite popular among the Gryffindors, as well as with many, many people in other Houses and with some of the teachers.
In the film adaptations, Fred and George are played by real life twins James Phelps and Oliver Phelps. Ironically, the Phelps twins are actually quite tall and lanky, which is the complete opposite of their physicality in the books, which is short and stocky.
You can find more in: http://en.wikipedia.org/wiki/George_and_Fred_Weasley

Upset!
I will be very upset if JKR kill one of these two boys! I totally love them! They are, after Ron, my favorite characters!
She won't kill them off.
She won't kill them off. They aren't main characters, and the next installment will make them a lot more serious.
Glad
I'm really glad J.K. Rowling included them in the books. They liven up the whole 'Voldemort' thing.
I agree that they probably
I agree that they probably won't be killed. They aren't main characters, so killing them wouldn't do a lot for the plot.
I also really like their characters. They definetely liven things up.