The 47-year-old actress and the 'Change-Up' star – who split from Scarlett Johansson after two years of marriage in December 2010 - are believed to have recently vacationed in Wyoming, and while on vacation the pair discussed the idea of marriage after the actor bonded with her 20-month-old son Louis.
A source told America's Star magazine: "Ryan told her he was ready to tie the knot whenever she wants. And after seeing how quickly she's bonded with baby Louis, she decided she's ready to pull the trigger, too.
"So they started discussing the logistics of pulling off a low-key, barefoot wedding that would reflect their laid-back lifestyle."
Scarlett – who was briefly linked to Sean Penn following her divorce from Ryan – is reported to be happy for the pair.
A source said: "Since Scarlett likes and respects Sandra so much, it doesn't bother her that she's with Ryan now."
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