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Tubi is probably the best free streaming option for the first three seasons of The Danny Thomas Show, but I think they only have a handful of episodes.

Pluto is probably the best free streaming option for My Three Sons.

Internet Archive, archive.org, has a great deal of My Three Sons, free viewing:

https://archive.org/details/mythreesonss01e01chipofftheoldblock

Once you become accustomed to navigating the site, you'll find so much.

The first three seasons of Danny Thomas (Make Room for Daddy) all went into public domain, probably because Danny didn't care. Word on the street was that he was upset when Jean Hagen left the show--which may have been why he didn't allow those seasons to go into local TV syndication.