On the tv show "The Waltons", who is older, Erin or Ben?

(The following is a cut and paste from a forum where presumably Eric Scott(who Ben Walton in the series) explains the discrepancy in the order of Erin Walton and Ben Walton birth order).

Post by ericscott on Jan 22, 2009 at 7:47am
Happy New Year everyone. The age thing again, huh?Remember, they casted us in a movie not a series. The part of Ben was originally two characters and in real life, I am closer to Judy's age and Mary and David are the same age so the original order was John Boy, Jason, Mary Ellen, Ben, Erin, Jim Bob, Elizabeth. Around the fourth year of the series, Ben and Erin switched. I talked with Grandma Ellen and she told me to stay young as long as possible so I encouraged the change. Hope this explains the discrepancies. Eric