The Other Weasleys (Arthur, Molly, Charlie, and Bill)They all have red hair, freckles, and more children than they can afford. They are a bit eccentric, all witches and wizards, and have what in today's society is generally referred to as monetary problems.
They're also ron's family, and thus quite important in the HP series. Arthur is ron's father. The architect of the Muggle protection act, he is fascinated and obsessed with Muggle products and collects batteries and plugs.
Molly, his wife, thinks he's mad, and to be perfectly honest, he is a bit that way inclined. He is incredibly Muggle-happy and even-tempered. He's also something of a softy - he lets gnomes populate his garden because he thinks they're funny and doesn't seem to like punishing his children or even speaking to them harshly.
Molly is something else altogether. Ron's mother, she can be very strict when the occasion demands, has a rather volatile tempermant, but, like all the Weasleys, is very nice to Harry. Of the non-Hogwarts attending Weasleys, she's probably the most important, being something of a mother-substitute for Harry.
Bill and Charlie are ron's two eldest brothers, both having completed schooling. Bill, a 'long haired pillock' (quote from the Daily Prophet, written by Rita Skeeter) works at Gringotts as a curse-breaker and Charlie studies dragons. Both were extremely good students in their time - Bill was head boy and Charlie Quidditch captain. They make their first major appearances in Book 4 but are never really that important.