Totally weird, I know, but hear me out. Obviously other species can drink each other's milk. In Milo and Otis, a kitten feeds from a pig. It's really cute. Has a human ever breastfed an animal? I would think if ANYONE in history has, it would be feeding a primate.
There was a women somewhere in Asia that was breastfeeding tiger cubs. They ended up dying. We had a farm cat that nursed an orphaned squirrel when we were kids. It was really cute and the squirrel survived.