Huh, I hadn't been aware there was an older brother.

I wonder if it's a reaction the producers get in the 'pilot' of a show. If the audience really doesn't like a character - off he goes and never existed.

I know I've seen several shows where the characters stay but the actor playing that character changes.

Very well known are the two Darrens on Bewitched and the switch of Becky in The Roseane Show.