https://www.yahoo.com/entertainment/tv/articles/john-eimen-child-actor-leave-000039066.html

He also was set to star as Jane Wyman’s son on another TV show before the Oscar-winning actress backed out.

That is very sad news

Here is a good picture of him in his chair

https://aaronbossig.wordpress.com/wp-content/uploads/2021/07/ff17c995-8cf0-4421-9483-eeaae531ee70.jpeg

It looks like he was credited in only one episode (S5 E37 - "Long Distance Call") of Leave it to Beaver as the 2nd Boy. Articles mention he was a classmate of Beaver in the first episode. I guess he was mostly in the background in any other episodes.

His big role was as Monk in 11 episodes of McKeever and the Colonel. He was active from 1958 to 1967.

I was surprised ABC World News Tonight mentioned him tonight. It sounds like he had a good life after his acting career ended.