Molly and Arthur
I'm away from my books at the moment so I can't work this one out! Were Molly and Arthur Weasley in the Original Order with Lily and James? Or was it just Molly's brothers?
According to Mad-Eye Moody in OotP when he shows Harry the picture, they were not in the picture, he only mentioned the brothers.
Originally Posted by Pheonix Tears
Then later in the same chapter, Lupin makes the comment that Molly wasn't in the Order last time.
From The Woes Of Mrs. Weasley, OotP.
I think they were too involved in the family, and Arthur starting at the Ministry. Not that they wouldn't have done it if asked, but with both of her brothers in the Order, and her growing family at home, I think neither of them would have thought to volunteer.
Hope that helps!
They were not in the original order, no. Remember, at the time, you're talking about 1978-1981. Bill was born in 1970, Charlie in 1972, Percy in 1976, the twins in 1978, Ron in 1980 and Ginny in 1981. Arthur was most likely in an even more junior position than he is now and was unlikely to have any free time.
It's also possible that Molly didn't support (at least not with manpower) what is effectively a vigilante group going after a group of terrorists, particularly after her brothers died, and that Arthur didn't care to go against the grain of the Ministry at the time, because he wouldn't want to risk his job, being as he had his family to think about. Being a sole breadwinner in a family that large is very stressful.