The 1979 movie Tim, starring Mel Gibson and DL fave Piper Laurie

Here's the link to watch on Amazon.

I’m in my forties and married to a 24 yo retarded man.

Not much of a stretch for Mel since Australian accents sound higly retarded.

I meant highly retarted

I saw this a few years back (don't ask why...) It's a total middle-aged frau fantasy: you, too, can own a hawt man who's functionally and intellectually a small child, but with a grown man's body. Be the lover AND the mommy. It's from the author of THE THORNBIRDS, so it's got the Frau-ness baked in.

I loathe MG but he's adorable in this. I was amused by their efforts to disguise Piper Laurie's, um, weight, which seems to fluctuate from scene to scene.

All of Colleen McCullough's romances are a bit creepy, OP.