Is this what I think it is? A swingers flag? They were also Shriners so there's a chance it's related to that
Yaah it's most likely a welcome flag. Were grandparents in the northeast? There are tons of them on flags and on homes up this way. Has to do with how difficult it was to get them in the 18th century so they were symbols of wealth and welcome.
The swinging thing I have never heard of, but then again, I don't pay attention to a lot of social stuff today.